He has been an umpire since 1995, working at all levels from the minor leagues to high school and everything in between. 

Weinstein began umpiring when he was twelve years old. He was with the Creve Coeur Athletic Association from 1995 to 2001. He started umpiring high school games while still a student at Parkway Central High School.

From 1998 to 2002, he was a member of the Greater St. Louis Association of Umpires, working high school, junior college, and college games.

In 2003, Weinstein umpired in Iowa in the Northwoods Summer Collegiate League. He was a minor league umpire from 2004 to 2008, working games in the Midwest League and the Carolina League. Many of the players would later advance to the Major Leagues. In 2005, he umpired the Midwest League all-star game. In 2006, he worked the Carolina League all-star game. In 2007, he was assigned to the Carolina League championship series.

From 2013 to 2022, Weinstein umpired in the Frontier League, an independent professional baseball league. In 2018, he was named Frontier League Umpire of the Year. In 2013, he joined the prestigious Collegiate Baseball Umpires Alliance, and he is still an active umpire with that organization, working NCAA games in several different conferences like the Big Ten and the Missouri Valley Conference. He also umpires junior college and NAIA games.

In 2002, he attended the Southern Umpires Camp, a training program for umpires in Atlanta, and he received the top award. 

For many years, Weinstein has mentored and trained younger umpires coming up through the ranks.