After service in the Royal Artillery during World War II, he worked as a surveyor for the Ordnance Survey, before commencing a full-time career as a climber, writer and photographer.

In 1950 he was a member of the first post-war Himalayan expedition and, in 1952, was one of the first to explore the previously closed mountain ranges of Nepal, east of Kathmandu.

From 1976–1987, he hosted the Scottish Television series Weir's Way, meeting the people of Scotland, exploring the landscape and its natural history.

[4] He is also celebrated in the song "Tom Weir" written by Edinburgh musician Sandy Wright and performed by the band Aberfeldy.

[citation needed] Weir was buried on 17 July 2006 in Kilmaronock Parish Church, near Drymen, in the same plot as the ashes of his sister Molly.