In 1930, Richardson had his first association with the Old Vic classical repertory company, remaining there and with the Sadlers Wells Company until 1932. He was prominent in the West End throughout the decade, toured the United States in 1935, and in 1938 played the lead in an Old Vic production of Othello. During World War 2, Richardson served in the Fleet Air Arm until 1944, like his friend Laurence Olivier. In that year, he and Olivier were released from service and instructed to help boost national morale by reviving the Old Vic company, which had been bombed out of its old premises. They were triumphantly successful, and at the (new) Old Vic, Richardson received wide acclaim for his interpretation of Peer in Ibsen's Peer Gynt.

Richardson's Falstaff in Shakespeare's Henry IV was received even more enthusiastically. In 1946, he went with the Old Vic on a tour of the United States, where the magazine Variety described his performance as "certainly unequalled in our days". Among those profoundly affected was the future literary critic Harold Bloom, then 16, who wrote, "the reality of Falstaff has never left me".