Finch and De Kock were among six overseas signings announced during Major League Cricket's (MLC) 'Domestic Player Draft' on Sunday, in which each of the six teams picked nine US-based players.
"So excited to be a part of @MLCricket @SFOUnicorns," tweeted Finch, who captained Australia in white-ball cricket before announcing his retirement from internationals last month.
The veteran will be joined by his former teammate Marcus Stoinis at the Unicorns as well as Victoria fast bowler Brody Couch, whose mother is American, making him eligible for the draft.
Fast bowler Liam Plunkett, who was part of the England side that won the 50-overs World Cup in 2019, was also picked by the Unicorns in the draft. Plunkett's wife is American.
De Kock, who previously captained South Africa across all three formats, will line up for the Orcas alongside Australia all-rounder Mitchell Marsh.
DC Freedom also announced two overseas signings, bringing in Sri Lankan spin bowling all-rounder Wanindu Hasaranga and South African fast bowler Anrich Nortje.
More overseas signings will be announced over the next few weeks.
In the draft, U.S. internationals Monank Patel and Steven Taylor were snapped up by MI New York, while former Canadian captain Nitish Kumar went to the Los Angeles Knight Riders.
The MLC tournament will be played between July 13-30 in Dallas.
