The Browns, who dismissed General Manager Phil Savage within hours of their 31-0 season-ending loss at Pittsburgh, dumped Crennel after he compiled a 24-40 record in four seasons.
Crennel's contract was through the 2011 season.
The Browns started the season with three straight losses and finished with a six-game losing streak during which they didn't score an offensive touchdown.
While the team gave no timetable or list of possible candidates for replacing Crennel, the name of former Browns linebacker and assistant coach Bill Cowher has cropped up. Cowher coached the Pittsburgh Steelers for 15 seasons, including six AFC championship games, eight division titles, 10 post-season berths and a win in Super Bowl XL.