Weiner joined the union staff as a lawyer in 1988 and replaced Don Fehr as its executive director in 2009. In 2011, Weiner led the union to agree to the Collective Bargaining Agreement that currently governs Major League Baseball. Weiner will likely be remembered in part for paving the way for punishments for the use of PEDs throughout the game. But he also helped negotiate the addition of a second Wild Card team, the move of the Houston Astros to the American League, the expansion of instant replay, and changes in team compensation for departing free agents.
In August 2012, it was reported that Weiner was being treated for a brain tumor, which turned out to be inoperable. He continued to work despite the diagnosis, keeping a full schedule even during the 2013 season. Weiner is survived by his wife, Diane, and three daughters.