Seager went 1-for-5 with a two-run home run in a 10-6 loss to Miami in the second game of Monday's doubleheader.
Seager, who surpassed his previous career high in home runs Aug. 28, reached the 30-homer mark in the seventh inning. The 28-year-old infielder has battled injuries during his career, but Seager has maintained good health in his first season with the Rangers.