The Mariners announced the move on Thursday. Earlier this week, third-base coach Jeff Datz announced he had been diagnosed with cancer and could be missing time while he seeks treatment options. The Mariners said Brown will be an extra coach and fill-in third-base coach when Datz is away.
Brown has been the manager of the Mariners' Triple-A affiliate in Tacoma and has worked as a manager in the Mariners farm system for the last 13 seasons.
Minor league catching coordinator John Stearns will take over as Tacoma's manager.