The actor, who plays Doug in the bromance comedy franchise, tied the knot with fitness trainer Lia Smith on Saturday, 4 January.
According to reports, the twenty or so guests at the sunset ceremony included his Hangover co-star Ken Jeong and actress Reese Witherspoon.
The nuptials took place at a ranch in Oahu and, thankfully, there don't seem to have been any Hangover-esque hijinks on the way to the altar e.g. missing members of the wedding party, borrowed tigers or severely sunburned grooms.
"They were sweet together and looked very in love," a source told Us Weekly. "He was holding her bouquet for her and walked with his arm around her after the vows. She had a big smile on her face and nuzzled her face up to his neck."
Justin, 35, confirmed his engagement in May 2013 but the couple have largely kept their romance out of the spotlight.
He previously dated Ashley Olsen for two years before they split in 2011.
Congrats to Justin and Lia!