Agent Malki Kawa confirmed the deal on social media, while Njoku thanked the Browns organization in a post to Instagram.
The Browns placed the franchise tag on Njoku earlier this offseason, and he had until July 15 to agree to a long-term contract. Had they not reached a deal, Njoku would've played the 2022 season on the franchise tender, which is worth $10.931 million, per a memo previously obtained by ESPN.
Njoku, 25, has totaled 148 receptions in five seasons with the Browns, including 36 catches for 475 yards and four touchdowns last season. His new deal will place him among the league's top five highest-paid tight ends.
His best season came during quarterback Baker Mayfield's rookie year in 2018, when he hauled in a career-best 56 catches for 639 yards. After being targeted 88 times that year, Njoku's targets decreased over the past three seasons.
The Browns, however, are banking that Njoku will thrive moving forward with new quarterback Deshaun Watson.
The Browns are now the only team in the NFL that have a quarterback (Watson), running back (Nick Chubb), wide receiver (Amari Cooper), and tight end (Njoku) that all rank in the top seven at their position in guaranteed money.
According to ESPN Stats & Information research, Njoku set career highs last season in yards per target and yards after catch per reception, showcasing the physical skills that made him the 29th overall pick in the 2017 draft.
Njoku ranked fourth in the league among tight ends in yards per target (9.0 yards) and tied for first in yards after the catch per target (6.7 yards).