in march 2018, the astros optioned kemp back to fresno. he was called up on may 16 to replace jake marisnick. in the 2018 season, kemp played in 97 games for the astros, batting .263/.351/.392 with 6 hr and 30 rbi, playing primarily in left field. he was mocked by the fenway park crowd and organist during the second game of the 2018 american league championship series (alcs) when he took an extended period of time to return to the batter's box after a foul ball. following the third game of the 2018 alcs, kemp received wide sports media coverage for making a leaping catch against the left field wall on a ball hit by steve pearce. the red sox challenged the catch at the wall, since it sounded like the ball hit the wall first. after further review, they announced the catch as confirmed, meaning the mlb replay crew in new york saw conclusive evidence of the catch. in game four, kemp hit a fourth inning solo home run off rick porcello after only hitting six homers during the regular season.