The Los Angeles Dodgers selected Smeltzer in the fifth round of the 2016 MLB draft and subsequently signed him to a one-year contract with a $500,000 signing bonus. He began his rookie season with the Arizona Dodgers, going 0-2 with a 7.59 ERA in 10.2 relief innings. In 2017, he began his professional career with the Great Lakes Loons of the Class A Midwest League, making ten starts. Afterwards, he made 15 appearances with the Rancho Cucamonga Quakes of the Class A-Advanced California League.