Born in Sydney, New South Wales, Alaalatoa played his junior football for the Bankstown Bulls before being signed by the Canterbury-Bankstown Bulldogs. He played for the Bulldogs' NYC team in 2008.

In 2012, Alaalatoa won the Terry Lamb Medal for the NSW Cup Player of the Year award and was also named at lock in the 2012 NSW Cup Team of the Year.

In Round 5 of the 2013 NRL season, Alaalatoa made his NRL debut for the Bulldogs against the Manly-Warringah Sea Eagles.