The Liberals were leading or elected in 25 of 32 electoral districts in Atlantic Canada by 8:30 p.m. EDT (0030 GMT on Tuesday) despite a drop in their overall popular vote from the 2015 election, according to the Canadian Broadcasting Corp.
Some Liberal losses had been expected in the region after Trudeau led the party to a clean sweep there four years ago. Atlantic Canada makes up less than 10% of the seats in the House of Commons.
The national race was expected to be closer as Trudeau, who took power as a charismatic figure promising "sunny ways," battles Conservative leader Andrew Scheer for the chance to form the next government.
Polls close in the vote-rich provinces of Ontario and Quebec at 9:30 p.m. EDT (0130 GMT on Tuesday). National voting is scheduled to end in the Pacific Coast province of British Columbia at 10 p.m. EDT (0200 GMT on Tuesday)