He managed the Triple-A Calgary Cannons from 1996 to 1997, the Nashville Sounds from 1998 to 2000 and 2003 to 2004, and when the Pirates changed their Triple-A affiliate from Nashville to Indianapolis, Jewett became the manager of the Indianapolis Indians from 2005 to 2008.

In 2009, Jewett began his first of two years as a manager in the Nationals' minor league system.

He led their High-A affiliate, the Potomac Nationals, in 2009 before being promoted to manage the Triple-A Syracuse Chiefs for 2010.

This was his only hiatus from minor-league managing until he joined the Nationals' major-league coaching staff in 2011.

On August 27, 2014, Jewett became interim manager for the weekend series against the Washington Nationals while Lloyd McClendon attended a wedding.