Allen, the defensive coordinator for the Denver Broncos last season, is to be on hand for a news conference Monday, the Raiders said on their Web site.
Allen, 39, replaces Hue Jackson, who was fired Jan. 10, the day Reggie McKenzie took over as the general manager at Oakland.
Before being hired Jan. 24, 2011, as the defensive coordinator at Denver, Allen was a defensive assistant at New Orleans for five seasons. His first NFL position was with the Atlanta Falcons from 2002-05.
Allen's defense in Denver was 20th in the NFL last season when the Broncos went 8-8 and had a tiebreaker advantage over the Raiders for a playoff berth. They eliminated Pittsburgh in a wild-card game but lost the following week to New England.
He will be the seventh Raiders head coach since Jon Gruden left after the 2001 season. Since then only Tom Cable, who was the coach for 44 games, lasted more than two seasons. Jackson was Oakland's coach for one season.