Simon Ward was born in Beckenham, the son of Winifred and Leonard Fox Ward, a car dealer. From an early age he wanted to be an actor. He was educated at Alleyn's School, London, the home of the National Youth Theatre, which he joined at age 13 and stayed with for eight years. Trained at the Royal Academy of Dramatic Arts, he made his professional stage debut with the Northampton Repertory in 1963 and his London theatrical debut one year later in The 4th of June. After the Royal Academy, he worked in repertory in Northampton, Birmingham and Oxford and occasionally in London's West End.

Ward married his wife, Alexandra Malcolm, in 1964, having met at RADA. They had three daughters, Sophie, Teresa and Kitty. His third and youngest daughter, Kitty, is married to British stand-up Comedian Michael McIntyre.

His big break in theatre came in 1967 when he played Dennis in Joe Orton's Loot, which led to a number of small film and television roles. All of Ward's major film roles were in the 1970s.

Persistent rumours suggest his first film appearance was an uncredited role as one of the sociopathic students in Lindsay Anderson's If.... (1968). Although this has never been verified, his participation in the film is still listed in his IMDb's actor's credits.

Simon Ward made few films after the 1970s, although he did have a major role in the Ralph Fiennes version of Wuthering Heights, made in 1992, alongside his daughter Sophie Ward.

In 1971, he played the title role of Winston Churchill in Young Winston. This was the role which brought him to national prominence and Ward starred in several high-profile films during the mid-to-late 1970s.

The following year he played the Duke of Buckingham in Richard Lester's The Three Musketeers (1973) and The Four Musketeers (1974), and also in 1974 he played author-veterinarian James Herriot in the successful film adaptation of All Creatures Great and Small. He played one of the lead roles (Lt. Crawford) in the 1976 World War I film Aces High, then starred as Lt. william Vereker in the 1979 film Zulu Dawn. He was also seen as Captain Hoffman, a fictional Nazi functionary, in Hitler: The Last Ten Days (1973). Later film roles included Zor-El in Supergirl (1984).

In 1986, Ward starred in the title role of Ross, the first West End revival of Terence Rattigan's play since its original run in 1960. It toured the UK and, after a run at the Royal Alexandra Theatre, Toronto, opened at The Old Vic, featuring Marc Sinden as Dickinson, with David Langton, Roland Curram, Bruce Montague and Ernest Clark in supporting roles.

In 1987 Ward suffered a serious head injury in a street attack that was never solved. He believed the attack, which left him with a broken skull that needed brain surgery, caused the chronic blood disorder, polycythaemia that affected his career.

In 1995, at very short notice, he took over Stephen Fry's role in the play Cell Mates, after Fry walked out of the play near the start of its run.

In 2001–07, he appeared as Sir Monty Everard in the BBC television series Judge John Deed and in 2007–10 as Bishop Stephen Gardiner in The Tudors.

In 2010, Ward appeared in the title role in the British tour of Alan Bennett's play The Madness of George III.

It was announced on 22 July 2012 that Ward had died after a long illness. His daughter Sophie stated that he had died "peacefully" on Friday 20 July with his family at his side.