Colorado Rockies president Keli McGregor was found dead in his Salt Lake City hotel room on Tuesday, the team said.
McGregor 48, was on a business trip with Rockies chairman and CEO Charlie Monfort and executive vice president Greg Feasel.
No details surrounding McGregor's death were immediately available.
"Words cannot describe the level of shock and disbelief that we all are feeling this morning at the loss of Keli," Monfort said in a statement.
"Our thoughts, our prayers are with (wife) Lori and the entire family as we all try to cope and understand how such a tragic loss could occur with such a wonderful man," he added.
The Rockies are 6-7 this year and are in the middle of a four-game series with the host Washington Nationals.
"On behalf of Major League Baseball, I am very saddened by the sudden and unexpected passing of Keli McGregor," MLB Commissioner Bud Selig said in a statement.
"As president of the Colorado Rockies, Keli was one of our game's rising young stars. He was a great athlete and equally great as a baseball administrator. Also, he was a great human being.
"All of baseball will miss him. I offer my condolences and deepest sympathies to his family, friends and the Rockies ball club," he added.