T20 Blast competition: Mohammad Amir set for Essex return
The 26-year-old left-arm quick helped Essex win the first-class County Championship in 2017 during a stint that saw him take career-best figures of 10 for 72 against Yorkshire at Scarborough.
Amir will be available for eight games in this year's Blast, including Essex's opener against Middlesex at Lord's on July 18.
"I'm very excited to return to Chelmsford and re-join my Essex team-mates," Amir told the county's website. "I thoroughly enjoyed my time here in 2017 and I'm looking forward to playing my role in the club's success this season."
Due to family commitments, Amir will miss the games against Surrey and Kent while his final match for Essex is set to be against Glamorgan on August 16.
Essex coach Anthony McGrath added: "Mo is one of the most exciting bowling talents in the world and I'm ecstatic he's going to be back with us."
Amir's career looked finished when he was given a five-year ban and jailed for involvement in a spot-fixing 'sting' during Pakistan's 2010 Test against England at Lord's.
But he returned to international cricket in 2016 and has now played 36 Tests, 49 one-day internationals and 42 T20s.