In the ballot, whose results were announced yesterday, 86.4% of T&G members gave the go-ahead for the merger and 70.1% of Amicus members voted for it.
Tony Woodley, T&G general secretary, said: "The new union will be a progressive, organising, fighting-back industrial giant focused above all on winning for our members in the workplace and talking trade unionism to the millions who need it."
The new union will come into existence on 1 May and preparatory work to choose a name is almost complete.
Amicus general secretary Derek Simpson said: "The new union will be the greatest campaigning force on behalf of ordinary people that has ever existed."
The new joint executive council, drawn equally from both unions, will supervise the drawing up of a final rule book.
This should come into effect in November 2008 when the integration of the two unions should be complete.
Woodley and Simpson will serve as joint general secretaries. A sole general secretary will be elected in a membership ballot in 2010.
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Amicus and T&G vote for superunion merger
Amicus and the Transport & General Workers' Union (T&G) have voted to merge to create Britain and Ireland's largest trade union with around 2m members.
