Washington Nationals outfielder Juan Soto earned the distinction in the National League.
Gurriel hit .423 with nine runs scored, four doubles, four home runs and 14 RBI over 17 games played in July. Among AL rookies with at least 20 at-bats over the month, Gurriel ranked first in hits and batting average; tied for first in RBI; second in home runs, on-base percentage and slugging percentage; and tied for fifth in extra-base hits.
The native of Cuba is the first Blue Jay to win the honour since Devon Travis in April 2015.
Gurriel was placed on the disabled list Wednesday due to a left high ankle sprain and a Grade 1 sprain of the left knee. He is expected to miss two-to-six weeks.
The 24-year-old was in the midst of an 11-game multi-hit streak before suffering the injuries. Gurriel is hitting .322/.340/.503 this season with seven home runs and 22 RBIs.