The casting director Marilyn Johnson, who has died aged 74, was universally loved by actors, producers and directors. It was her job to put performers in front of those making productions for television and film, and she was admired for her ability to help all of them feel comfortable in a meeting room.

She had an eye for new talent, and many actors credited her with giving them their break. One of her greatest triumphs during a time of greater risk-taking in television was spotting three unknowns – Ann Mitchell, Maureen O’Farrell and Fiona Hendley – to star in the six-part ITV drama Widows (1983). The story of three women carrying out an armed robbery that their husbands had been killed attempting, it was Lynda La Plante’s first success as a writer for television.

When Johnson worked on the 1995 series of Cracker, starring Robbie Coltrane as the flawed criminal psychologist Dr Edward “Fitz” Fitzgerald, she paired John Simm and Liam Cunningham in one story to create electrifying performances as a murderous duo.

Later, with the sitcom Vicious (2013-16), it was her idea to feature three veterans who were household names – Ian McKellen and Derek Jacobi as the couple who have been together for half a century, along with Frances de la Tour as their man-chasing friend.

At other times, Johnson would be asked to build a cast around a star. When A Touch of Frost (1992-2010) was conceived as a vehicle for David Jason to transform from comedy to drama in the role of the scruffy detective featured in RD Wingfield’s novels, she was responsible for providing solid support from Bruce Alexander as Detective Inspector Jack Frost’s by-the-book boss, Superintendent Norman Mullett, and John Lyons as his sidekick, Detective Sergeant George Toolan, as well as guest stars and other character actors. A particular challenge was ensuring that many of them were shorter than the 5ft 6in Jason so that he was not constantly looking up.

Marilyn was born in Oxford, the daughter of William Johnson, a London department store manager, and Evelyn (nee Patterson). The family moved around and, on leaving Wesley college, Dublin, Johnson took secretarial jobs in London before working as a receptionist at the advertising agency Saatchi & Saatchi, where she gained experience on commercials with the casting director Allan Foenander.

He encouraged her to turn freelance and she eventually moved from commercials – where she worked with the director Ridley Scott – to films and television programmes, starting with the 1971 Children’s Film Foundation production Danger Point!, with a cast that included Hattie Jacques.

Her breakthrough came when she had the chance to work on the last two series (1976 and 1978) of The Sweeney, as well as its two spin-off films (1977 and 1978). For almost 40 years, her credit was a familiar one, appearing at the end of nearly 100 different TV movies or series.

Johnson had crucial casting jobs on programmes at their inception, including dramas such as Boon (1986), featuring Michael Elphick as a firefighter-turned-courier, minder and private investigator; 99-1 (1994), a post-EastEnders vehicle for Leslie Grantham; Murphy’s Law (2003), with James Nesbitt as a maverick detective; and Diamond Geezer (2005), starring Jason. She also worked on the romantic sitcom As Time Goes By (1992), with Judi Dench and Geoffrey Palmer, and the comedy-dramas Micawber (2001), again with Jason, and Honest (2008), starring Amanda Redman.

Johnson was also adept at finding supporting cast for established series, such as Van der Valk (the 1977 and 1992 runs), Inspector Morse (between 1989 and 2000), Lovejoy (in 1991-92) and Stay Lucky (in 1993), and she worked on several feature films: The Bitch (1979), McVicar (1980), in which her casting included the future Bill and EastEnders star Billy Murray as Joey Davis, who hides the famed armed robber after his escape from prison, and 84 Charing Cross Road (1987).

When TV producers and directors had ideas of filling roles with actors they had previously used, Johnson would sometimes steer them in a new direction, which both saved viewers from seeing the same old faces and gave opportunities to up-and-coming performers.

Her friends and colleagues described her as fun to be around and she is remembered as being positive in the most testing circumstances – and for her commitment to finding the right artists. When a 1995 Touch of Frost story featured young people with Down’s syndrome, she not only drove hundreds of miles to meet many in theatre companies for those with disabilities, but also insisted that donations should be made to the groups.

In 2002, Johnson married Ahmed Sanna, a restaurateur, who died in 2012. She is survived by her partner, Eric Burden.

• Marilyn Elizabeth Florence Johnson, casting director, born 12 June 1944; died 12 August 2018