Following the ball-tampering incident in South Africa, and the subsequent nine-month ban for Renshaw's international team mate Cameron Bancroft, Renshaw was signed to replace Bancroft as an international player at Somerset County Cricket Club for the 2018 English cricket season. He made his debut for Somerset on 20 April 2018 against Worcestershire, scoring 101 not out, exactly half of Somerset's first innings total of 202, and went on to score 513 runs at an average of 51.13 in six Championship matches for the county, scoring another century in his second match. He also scored 180 runs in six List A appearances for Somerset before his spell at the county was cut short following a broken finger.