Kemp earned the National League honors while leading major league baseball in home runs (12) and batting average (.417) after one month of play.
He also topped the NL in hits (35), RBI (25), runs (24) and slugging percentage (.893).
His performance has sparked Los Angeles to its best start since 1983 with a 16-7 record.
Hamilton, meanwhile, claimed the American League award with a .395 average for the month, during which the Rangers outfielder collected a league-best nine home runs and 25 RBI.
He notched hits in 13 of his first 14 games during April, including four straight multi-hit games.