Dennard, 24, reported to the Lancaster County Adult Detention Facility Saturday morning, according to corrections officers with the Lincoln facility who spoke on condition of anonymity because of jail policy.
The former Nebraska football standout will have to serve at least 35 days, after credit for good behavior and the three days he's already spent in jail.
In April, a judge sentenced Dennard to two years' probation, 30 days in jail and community service for assaulting an officer and resisting arrest outside a Lincoln bar days before he was chosen in the NFL Draft. Dennard had been projected to be a middle-round NFL draft pick, but the Patriots took him in the seventh round.
The judge later extended his probation to three years and doubled the jail time after Dennard was again arrested in Lincoln on suspicion of drunken driving in July. That charge was later dismissed in exchange for Dennard's no contest plea for refusing to submit to a chemical test. He was fined $500 and placed on probation for that offense.
Dennard finished this season, his second in the NFL, with 40 tackles (34 solo, 6 assists) and one interception. The Patriots fell just short of the Super Bowl, losing to the Denver Broncos in the AFC Championship game.