According to Shams Charania of Yahoo Sports, Jennings' second 10-day pact with the team expired Friday.
In 10 games with the Bucks this season, Jennings has averaged 5.5 points, 3.3 assists and 2.1 rebounds. He's also shot 38.8 percent from the field.
After a stint in the Chinese Basketball Association, Jennings joined the Bucks' G League affiliate, the Wisconsin Herd.
He played well for the Herd and has reportedly parlayed that into a standard contract with the Bucks.
Milwaukee selected the 28-year-old with the No. 10 overall pick in the 2009 NBA draft.
His best season came in 2011-12 when he averaged a career-high 19.1 points per game with the Bucks.
Jennings has primarily been a bench player in recent years, and he will continue to provide much-needed backcourt depth behind Eric Bledsoe and Tony Snell, as Malcolm Brogdon (quad) and Matthew Dellavedova (ankle) work their way back from injuries.