Terry Molloy has been a member of the cast of BBC Radio 4's The Archers playing Mike Tucker since 1973 and has won awards for his work as an actor on radio. In 1980 he performed in the Radio 4 adaptation of Nicholas Monsarrat's war novel The Cruel Sea.

On television, Molloy is perhaps best known for becoming the third actor to play the mad scientist Davros, the creator of the Daleks, in the long-running science fiction series Doctor Who. He appeared in the stories "Resurrection of the Daleks", "Revelation of the Daleks", and "Remembrance of the Daleks", becoming the first actor to play the role in different stories. Molloy was initially cast in the role by director Matthew Robinson, who had worked with him before and thought his talent for voices would be ideal to recreate the part first played by Michael Wisher. Molloy also appeared in the Doctor Who story "Attack of the Cybermen" as an undercover policeman named Russell.

In recent years, Molloy has reprised the role of Davros in the Big Finish Productions audio dramas "Davros", "The Juggernauts", "Terror Firma", "Masters of War", "The Davros Mission", and the four-part miniseries "I, Davros". He also played Davros in a 2005 stage production, The Trial of Davros. Molloy also took over the role of Stan Harvey in the ITV soap opera Crossroads from Edward Clayton when Stan made a brief visit to the motel in 1987.

Molloy regularly attends Doctor Who conventions and events, where he meets fans and speaks about his time on the program. He also appeared on BBC 7 in the role of Professor Edward Dunning opposite fellow Doctor Who actor Nicholas Courtney in The Scarifyers audio series.

In 2014 he voiced Davros in Benjamin Maio Mackay's touring comedy show "50 Years of Doctor Who: Preachrs Podcast Live 2!" which played Adelaide Fringe and Melbourne International Comedy Festival to great acclaim.