Before World War I, Walter Owen Bentley and his brother, Horace Millner Bentley, sold French DFP cars in Cricklewood, North London, but W.O, as Walter was known, always wanted to design and build his own cars. At the DFP factory, in 1913, he noticed an aluminium paperweight and thought that aluminium might be a suitable replacement for cast iron to fabricate lighter pistons. The first Bentley aluminium pistons were fitted to Sopwith Camel aero engines during World War I.

Rolls-Royce took over the assets of Bentley Motors (1919) Ltd and formed a subsidiary, Bentley Motors (1931) Ltd. Rolls-Royce had acquired the Bentley showrooms in Cork Street, the Service station at Kingsbury, the complex at Cricklewood and the services of Bentley himself. This last was disputed by Napier in court without success. Bentley had neglected to register their trademark so Rolls-Royce immediately did so. They also sold the Cricklewood factory in 1932. Production stopped for two years, before resuming at the Rolls-Royce works in Derby. Unhappy with his role at Rolls-Royce, when his contract expired at the end of April 1935 W. O. Bentley left to join Lagonda.

Bentley's first major event was the 1922 Indianapolis 500, a race dominated by specialized cars with Duesenberg racing chassis. They entered a modified road car driven by works driver, Douglas Hawkes, accompanied by riding mechanic, H. S. "Bertie" Browning. Hawkes completed the full 500 miles (800 km) and finished 13th with an average speed of 74.95 miles per hour (120.62 km/h) after starting in 19th position. The team was then rushed back to England to compete in the 1922 RAC Tourist Trophy.

The Bentley enterprise was always underfunded, but inspired by the 1924 Le Mans win by John Duff and Frank Clement, Barnato agreed to Finance Bentley's Business. Barnato had incorporated Baromans Ltd in 1922, which existed as his Finance and investment vehicle. Via Baromans, Barnato initially invested in excess of £100,000, saving the Business and its workforce. A financial reorganisation of the original Bentley company was carried out and all existing creditors paid off for £75,000. Existing shares were devalued from £1 each to just 1 shilling, or 5% or their original value. Barnato held 149,500 of the new shares giving him control of the company and he became chairman. Barnato injected further cash into the business: £35,000 secured by debenture in July 1927; £40,000 in 1928; £25,000 in 1929. With renewed financial input, W. O. Bentley was able to design another generation of cars.

In an ironic reference to his heavyweight boxer's stature, Captain Woolf Barnato was nicknamed "Babe". In 1925, he acquired his first Bentley, a 3-litre. With this car he won numerous Brooklands races. Just a year later he acquired the Bentley Business itself.

The Bentley Boys were a group of British motoring enthusiasts that included Barnato, Sir Henry "Tim" Birkin, steeple chaser George Duller, aviator Glen Kidston, Automotive Journalist S.C.H. "Sammy" Davis, and Dudley Benjafield. The Bentley Boys favoured Bentley cars. Many were independently wealthy and many had a military background. They kept the marque's reputation for high performance alive; Bentley was noted for its four consecutive victories at the 24 Hours of Le Mans, from 1927 to 1930.

In 1929, Birkin developed the 4½-litre, lightweight Blower Bentley at Welwyn Garden City and produced five racing specials, starting with Bentley Blower No.1 which was optimised for the Brooklands racing circuit. Birkin overruled Bentley and put the model on the market before it was fully developed. As a result, it was unreliable.

Bentley withdrew from motor racing just after winning at Le Mans in 1930, claiming that they had learned enough about speed and reliability.

All Bentleys produced from 1931 to 2004 used inherited or shared Rolls-Royce chassis, and adapted Rolls-Royce engines, and are described by critics as badge-engineered Rolls-Royces.

When the new Bentley 3½ litre appeared in 1933, it was a sporting variant of the Rolls-Royce 20/25, which disappointed some traditional customers yet was well received by many others. W. O. Bentley was reported as saying, "Taking all things into consideration, I would rather own this Bentley than any other car produced under that name". Rolls-Royce's advertisements for the ​3 ⁄₂ Litre called it "the silent Sports car", a slogan Rolls-Royce continued to use for Bentley cars until the 1950s.

Barnato received £42,000 for his shares in Bentley Motors. In 1934 he was appointed to the board of the new Bentley Motors (1931) Ltd. In the same year Bentley confirmed that it would continue racing.

In preparation for war, Rolls-Royce and the British Government searched for a location for a Shadow factory to ensure production of aero-engines. Crewe, with its excellent road and rail links, as well as being located in the North West away from the aerial bombing starting in mainland Europe, was a logical choice. Crewe also had extensive open farming land. Construction of the factory started on a 60-acre area on the potato fields of Merrill's Farm in July 1938, with the first Rolls-Royce Merlin aero-engine rolling off the production line five months later. 25,000 Merlin engines were produced and at its peak, in 1943 during World War II, the factory employed 10,000 people. With the war in Europe over and the general move towards the then new jet engines, Rolls-Royce concentrated its aero engine operations at Derby and moved motor car operations to Crewe.

To meet post-war demand, particularly UK Government pressure to export and earn overseas currency, Rolls-Royce developed an all steel body using pressings made by Pressed Steel to create a "standard" ready-to-drive complete saloon car. The first steel-bodied model produced was the Bentley Mark VI: these started to emerge from the newly reconfigured Crewe factory early in 1946. Some years later, initially only for export, the Rolls-Royce Silver Dawn was introduced, a standard steel Bentley but with a Rolls-Royce radiator grille for a small extra charge, and this convention continued.

The early R Type Continental has essentially the same engine as the standard R Type, but with modified carburation, induction and exhaust manifolds along with higher gear ratios. After July 1954 the car was fitted with an engine, having now a larger bore of 94.62 mm (3.7 in) with a total displacement of 4,887 cc (4.9 L; 298.2 cu in). The compression ratio was raised to 7.25:1.

Chassis remained available to coachbuilders until the end of production of the Bentley S3, which was replaced for October 1965 by the chassis-less monocoque construction T series.

The problems of Bentley's owner with Rolls-Royce aero engine development, the RB211, brought about the financial collapse of its Business in 1970.

The motorcar division was made a separate Business, Rolls-Royce Motors Limited, which remained independent until bought by Vickers plc in August 1980. By the 1970s and early 1980s Bentley sales had fallen badly; at one point less than 5% of combined production carried the Bentley badge. Under Vickers, Bentley set about regaining its high-performance heritage, typified by the 1980 Mulsanne. Bentley's restored sporting image created a renewed interest in the name and Bentley sales as a proportion of output began to rise. By 1986 the Bentley:Rolls-Royce ratio had reached 40:60; by 1991 it achieved parity.

In October 1997, Vickers announced that it had decided to sell Rolls-Royce Motors. BMW AG seemed to be a logical purchaser because BMW already supplied engines and other components for Bentley and Rolls-Royce branded cars and because of BMW and Vickers joint efforts in building aircraft engines. BMW made a final offer of £340m, but was outbid by Volkswagen AG, which offered £430m. Volkswagen AG acquired the vehicle designs, model nameplates, production and administrative facilities, the Spirit of Ecstasy and Rolls-Royce grille shape trademarks, but not the rights to the use of the Rolls-Royce name or logo, which are owned by Rolls-Royce Holdings plc. In 1998, BMW started supplying components for the new range of Rolls-Royce and Bentley cars—notably V8 engines for the Bentley Arnage and V12 engines for the Rolls-Royce Silver Seraph, however, the supply contract allowed BMW to terminate its supply deal with Rolls-Royce with 12 months' notice, which would not be enough time for Volkswagen to re-engineer the cars.

BMW paid Rolls-Royce plc £40m to license the Rolls-Royce name and logo. After negotiations, BMW and Volkswagen AG agreed that, from 1998 to 2002, BMW would continue to supply engines and components and would allow Volkswagen temporary use of the Rolls-Royce name and logo. All BMW engine supply ended in 2003 with the end of Silver Seraph production.

In 2002, Bentley presented Queen Elizabeth II with an official State Limousine to celebrate her Golden Jubilee. In 2003, Bentley's two-door convertible, the Bentley Azure, ceased production, and Bentley introduced a second line, Bentley Continental GT, a large luxury coupé powered by a W12 engine built in Crewe.

From 1 January 2003 forward, Volkswagen AG would be the sole provider of cars with the "Bentley" marque. BMW established a new legal entity, Rolls-Royce Motor Cars Limited, and built a new administrative headquarters and production facility for Rolls-Royce branded vehicles in Goodwood, West Sussex, England.

Bentley sales continued to increase, and in 2005 8,627 were sold worldwide, 3,654 in the United States. In 2007, the 10,000 cars-per-year threshold was broken for the first time with sales of 10,014. For 2007, a record profit of €155 million was also announced. Bentley reported a sale of about 7,600 units in 2008. However, its global sales plunged 50 percent to 4,616 vehicles in 2009 (with the U.S. deliveries dropped 49% to 1,433 vehicles) and it suffered an operating loss of €194 million, compared with an operating profit of €10 million in 2008. As a result of the slump in sales, production at Crewe was shut down during March and April 2009. Though vehicle sales increased by 11% to 5,117 in 2010, operating loss grew by 26% to €245 million. In Autumn 2010, workers at Crewe staged a series of protests over proposal of compulsory work on Fridays and mandatory overtime during the week.

Demand had been so great that the factory at Crewe was unable to meet orders despite an installed capacity of approximately 9,500 vehicles per year; there was a waiting list of over a year for new cars to be delivered. Consequently, part of the production of the new Flying Spur, a four-door version of the Continental GT, was assigned to the Transparent Factory (Germany), where the Volkswagen Phaeton luxury car is also assembled. This arrangement ceased at the end of 2006 after around 1,000 cars, with all car production reverting to the Crewe plant.

A limited run of a Zagato modified GT was also announced in March 2008, dubbed "GTZ".

A new version of the Bentley Continental was introduced at the 2009 Geneva Auto Show: The Continental Supersports. This new Bentley is a supercar combining extreme power with environmentally friendly FlexFuel Technology, capable of using petrol (gasoline) and biofuel (E85 ethanol).

After acquiring the Business, Volkswagen spent GBP500 million (about US$845 million) to modernise the Crewe factory and increase production capacity. As of early 2010, there are about 3,500 working at Crewe, compared with about 1,500 in 1998 before being taken over by Volkswagen. It was reported that Volkswagen invested a total of nearly US$2 billion in Bentley and its revival. As a result of upgrading facilities at Crewe the bodywork now arrives fully painted at the Crewe facility for final assembly, with the parts coming from Germany—similarly Rolls-Royce body shells are painted and shipped to the UK for assembly only.

Unsold cars: During the years 2011 and 2012 production exceeded deliveries by 1,187 cars which is estimated to have trebled inventory.

A Bentley Continental GT3 entered by the M-Sport factory team won the Silverstone round of the 2014 Blancpain Endurance Series. This was Bentley's first official entry in a British race since the 1930 RAC Tourist Trophy.