The NHL expansion club announced the moves Saturday.
Reinhart has 37 games of NHL experience with Edmonton and the New York Islanders, who drafted him with the fourth overall pick in 2012. Vegas signed him to a two-year, $1.6 million deal.
Leipsic appeared in his first six NHL games during the 2015-16 season with Toronto. He got a two-year, $1.3 million contract with the Golden Knights.
Vegas also signed forward Cody Glass, forward Nick Suzuki and defenseman Erik Brannstrom to three-year, entry-level contracts. Glass was the sixth overall pick last month, while Suzuki was 13th and Brannstrom went 15th.