He was a marked modernist and was for 22 years a leading vice Mayor of Stockholm, in charge of urban development, and politically leading behind several of the city's largest urban development projects of the 20th century, including Slussen, Stockholm Metro and the major redevelopment of Norrmalm borough in central Stockholm. Larsson's role in the post-war planning of Stockholm and its new suburbs was internationally recognized. The American city planner Clarence Stein wrote that:
They have developed an organization for city building that is second only to that of the London County Council. But it differs from that in having a broader, more complete goal and ideal. This has been due I think largely to Yngve Larsson's statesmanship; also to his sympathetic understanding with Markelius and Sidenbladh as architect-planners, and with Holger Blom (an architect, too), who makes the parks throughout Stockholm rich with blooming color.