Day will represent the International side for the fifth time. He missed out on an automatic qualifying spot by fewer than four points.
Hadwin previously played in the 2017 Presidents Cup while Im and Niemann will make their debuts in the team competition. The International team will send six rookies to Australia's Royal Melbourne Golf Club to take on the heavily favored Americans.
Here is the final roster for the International squad:
* Denotes Presidents Cup rookie
Tiger Woods will make his selections for Team USA on Thursday at 7:00 p.m. ET.
The four-day team event begins Dec. 12.