Rivers, 28, began the season on the New York Knicks but was traded to the Oklahoma City Thunder as part of a three-team deal that also involved Philadelphia at the trade deadline. The Thunder waived him, as Rivers was not a part of the Thunder's future plans.
He brings size and shooting to Denver's backcourt, along with plenty of playoff experience -- 45 games with the Clippers and Rockets. He is eligible for Denver's playoff roster because he wasn't on an NBA roster after April 9.
Rivers joins a Nuggets team that is fourth in the Western Conference and has won three straight games but faces a difficult path through the playoffs without star point guard Jamal Murray. A torn ACL ended Murray's season earlier this month.
Rivers, who is expected to be available Wednesday, figures to enter a point guard rotation that also includes Facundo Campazzo, PJ Dozier and Shaquille Harrison. Monte Morris had assumed Murray's role as the team's starting point guard, but is now battling a hamstring injury that coach Mike Malone said will sideline Morris for "a little while." However, much of Denver's offense runs through center and MVP candidate Nikola Jokic, who leads the team in points (26.4), rebounds (11.1) and assists (8.8) per game.
Rivers is averaging 7.3 points, 2.2 rebounds and 2.0 assists this season in 21 games with New York.
The Nuggets will be the sixth team Rivers has actually suited up for. Selected 10th overall by New Orleans in the 2012 draft, Rivers has also played for the Clippers, Rockets (twice) and Washington Wizards before signing with the Knicks.
Information from The Associated Press was used in this report.