Adams made his professional acting debut in the 1984 horror film A Nightmare on Elm Street.

In 1986, the casting Director at ABC's Ryan's Hope announced that they were looking to cast an adult actor to take over the role of John Reid Ryan on the soap. Adams came in to read and won the part, of which he played from August 1986 until the show's final episode on January 13, 1989. His character had previously been a child for RH's first decade on the air (known as "Little John Ryan" and later "Johnno Ryan", and played from newborn stage to age 10 by Jadrien Steele, from 1975–1985). Adams is known for being one of the earliest soap actors brought into take over a role due to SORAS-ing (Soap Opera Rapid Aging Syndrome).

ABC cast him as the lead in a two-hour movie pilot they were considering to pick up as a weekly series, Thunderboat Row. Even though the movie was well received, it never became a series. This was followed by a guest shot on the syndicated revival of Adam-12, just before he was cast as François Gaultier in Lionheart (1990), alomgside Jean-Claude Van Damme. On the heels of Lionheart's success at the box office, Adams was catapulted into heavier movie roles in The Arc (1991), Original Intent (1992), the indie flick I'll Love You Forever..Tonight (1992), the cult horror favorite Puppet Master 4 (1993) and into an appearance in the short The Privilege Cage (1994). Occasionally during this time, Adams still turned up in some guest roles, including in two episodes of ABC's The Young Riders in 1990, playing Jeffrey Darnell.

Subsequent movie roles for Adams included Deputy Steve Stowe in The Stranger (1995), a cameo in Mother (1996), and a large part in Striking Resemblance (1997). He continued to appear in guest shots on popular cable and syndicated series, including an episode of Renegade in 1997, and on Pamela Anderson's V.I.P. in 1999. By this time he was now going professionally by Ash Adams (for reasons discussed below), but despite the change in his stage name, in certain credits of his listed above from 1996 or later, he continued to be credited as Jason Adams.

In 1996, Adams decided to start using the longtime nickname of "Ash" professionally in place of Jason. The switch came about as a result of increasing confusion among viewers, fans, Screen Actors Guild officials and others in the media between certain credits of his and those of a newer, up-and-coming actor, Jason Leland Adams (to whom he is not related). When the latter Adams entered the SAG for the first time, he immediately had to register his middle name of Leland in from the start since the former Jason Adams already existed in their index. However, despite the fact that the first Jason Adams had already been a known face in Hollywood for the past decade, announcements of new projects with the newer Jason (Leland) Adams in the cast automatically led people to think it was the first Jason, since not all casting sources adhered to the proper SAG listing of the newer Jason's name. The situation became even more convoluted when other records began erroneously listing the first Jason Adams' middle name as being Leland, when in fact it never was. Finally, the original Jason Adams decided to ease the situation by dropping his real first name altogether, and becoming Ash Adams.

In the early 2000s, Adams put aside time to specifically focus on live theatre work, at first committing to popular productions at the Actors Studio in New York City. It was there where he starred in Mass Appeal and Return to the Chicago Abyss. He later returned to the Los Angeles area to star in the local production of Hurly Burly in 2004. In between the latter two plays, he made a guest appearance in an early episode of ABC's 2003 revival of Dragnet. The most important development in Adams' career outside of his acting at this time was his preparation for a filmmaking career. Before he had finished his stage work in New York City, Adams had already started raising funds for an inaugural movie project of his own, while launching a production company which ultimately became his independent film marque Bravado Pictures.

In 2003, Adams launched his production company Bravado Pictures along with his first original independent film, After the Past. The maiden project, like all of Ash's Future efforts was written, produced and directed by himself, along with featuring Adams in a prominent on-screen role. Here, he was the top-billing star. The movie was co-produced by Oscar-nominated Actress Amy Madigan, who in addition functioned as narrator of After the Past. The plot centered around two brothers, played by Adams and Branden Morgan, who reunite at the funeral of their abusive father. As the story unfolds, they try and come to terms with the death of their mother, the violence that was put on them as children and the damage they are left with as adults. Production was complete by mid-2003 and prior to its official release, set for the following year, the public was given a full-length preview screening at the 2003 Malibu International Film Festival. The audience reaction to After the Past was extremely positive, and it ended up winning the 2003 Audience Choice Award at the festival. Entertainment Today reviewed the film and noted that After the Past was "an impressive debut for Actor/Writer/Director Ash Adams." The movie went on to compete in all other major US film festivals per its official release in 2004.

The film was in production starting in late 2004 and during most of 2005, before its official release at the Roving Eye Documentary Film Festival in 2006. The Distance won the Roving Eye festival, thanks to in part of the movie's star power and the attention it received while in production. This does not take away from the fact that it was the raw, gripping emotion of Adams' storytelling that earned The Distance its merit; his raised profile as a filmmaker caused the film to be picked up by the Ohio Independent Film Festival not long after. In Ohio, The Distance continued to be the darling of audiences and critics alike, and received a second nomination for Best Documentary. During this stage of its run, Julie Washington of The Plain Dealer called The Distance "heartbreaking and unforgettable". The momentum built up from its nominations and win, combined with the heavy star power and critical buzz within the industry it was receiving, allowed The Distance to then travel abroad and compete internationally. Later in 2006, it was screened at the Montreal World Film Festival, the John Huston Puerto Vallarta Film Festival and at the Rhode Island International Film Festival. The Distance became Adams' first widespread success, and such a distinction was topped off when Image Entertainment acquired the film for mass distribution. It was released on DVD in late 2006.

In February 2007, Adams met with Bill Via, founder of the independent film and music site Indieoma.com, and proposed the idea of developing an online series to add to the fledgling site which would explore the world of independent filmmaking from the inside out. Indieoma.com, which launched in January 2007, is a site that promotes new releases from well-known artists in the landscape of independent media, as well as allowing budding artists to create accounts and showcase their work in hopes of gaining attention from the insiders. Adams decided to bank on the new site, since its Future seemed promising with the involvement it had from other Hollywood-types; he promptly started at blog on Indieoma the same month he began series development with Via, in which he began connecting with the public, especially with those who had been fans of his recent success The Distance. In April 2007, Ash announced that his upcoming series on Indieoma would be titled Mavericks, a one-on-one interview series in which he would sit down with screen legends who had been hailed for their indie film performances in addition to their bigger-budget successes.

From its inception, Mavericks has been produced by Adams, Bill Via, and Michael Madsen, who was Adams' first guest on the series. Between April and June 2007, Adams had stated in his blog entries that Mavericks was to debut in June, but at the last minute, he and Via decided to hold off on the debut so they could work on the format further. After a year of reworking the format, Mavericks premiered on the week of March 22, 2008. Each installment of the program is in four parts, and has one guest actor per show. Michael Madsen was the first guest, as scheduled; subsequent editions have had Ash sit down with actors he has worked with recently at Bravado Pictures, including Amy Madigan and Andy Dick, while Veronica Cartwright and Taylor Negron have been other subjects.