The decision was made by the union’s executive council following interviews with all the candidates.
Ucatt is asking its members to cast their first preference vote for leader for Andy Burnham and their second preference for veteran left-winger Jeremy Corbyn.
Ucatt is also nominating Angela Eagle for deputy leader, with Tom Watson as its second preference.
National secretary Brian Rye said Andy Burnham “understands the concerns of workers and has all the credentials to be prime minister”.
He said: “Ucatt is particularly impressed by Burnham’s policies on housebuilding, vastly increasing the number of genuine apprenticeships and insuring that wage rates in industries such as construction are not undercut.”
Mr Rye added: “Angela Eagle has the experience, knowledge and maturity to make an excellent deputy leader. She is respected and liked throughout the Labour movement.”
Bookmakers have Andy Burnham as the clear favourite to be next Labour Party leader. William Hill and Paddy Power both put him currently at 5/6 while Ladbrokes offers only 10/11.
The result is due to be announced on 12th September 2015.