In two seasons with the Patriots, LaFell caught 111 passes and scored seven touchdowns, but his role diminished greatly in 2015 and he was released March 2.
The Bengals' hope for LaFell is that he will replace receiver Mohamed Sanu. A versatile pass-catcher who has spent nearly 40 percent of his time in the league as a slot receiver, LaFell is expected to fill Sanu's old role. Like receiver Marvin Jones, Sanu left Cincinnati in free agency earlier this month. Sanu signed with the Atlanta Falcons while Jones signed with the Detroit Lions.
With LaFell's signing, the Bengals now have the flexibility to select any position in the first round of next month's draft, though they still might use that pick on a receiver. They need to find a replacement for Jones, and there are early-round prospects who have similar playing styles. TCU's Josh Doctson and Ohio State's Michael Thomas are two players the Bengals have reportedly expressed interest in.
LaFell had a career year with the Patriots in 2014, his first season with the club, totaling 74 receptions for 953 yards and seven touchdowns. He started 13 of 16 games during the regular season and then all three playoff contests, adding 13 catches for 119 yards and two touchdowns in the playoffs.
An injury to his left foot, however, affected his offseason, and he opened 2015 on the physically unable to perform list. LaFell never seemed to find his groove upon his return, finishing this past season with 37 catches for 515 yards and no touchdowns. He played in 11 games with seven starts.
The 29-year-old saw his role scaled back over the course of the 2015 season, slipping to the No. 4 spot on the depth chart for the AFC Championship Game. Before joining the Patriots, he spent four seasons with the Carolina Panthers after entering the league as a third-round draft choice in 2010. With the Panthers, he caught 167 passes for 2,385 yards and 13 touchdowns.
ESPN's Adam Schefter, Coley Harvey and Mike Reiss contributed to this report.