Washington is 62-85 and has improved from last season, when it went 59-103. It was Riggleman who brought accountability back into the Nationals' clubhouse for the first time since Frank Robinson managed the club from 2002-06.
General manager Mike Rizzo praised Riggleman on Saturday for the job he has done this season.
"I like the way he has handled the team this year, and he is a good manager," Rizzo said. "With the real turbulent year this year -- from the highs and the lows -- he has really balanced it out. He has respect of the clubhouse.
"When it comes to X's and O's, he is as good as anybody. He has worked hard during trying circumstance. He has managed young players who are getting better and learning on the Major League level and have shown improvement on the Major League level. That is a positive."
Riggleman replaced Manny Acta as manager of the Nationals after the All-Star break last season. The club went 33-42 and finished the year on a seven-game winning streak.
This is Riggleman's fourth managerial stint, after leading the Padres, Cubs and Mariners. His best season as a skipper was in 1998, when he guided the Cubs to the playoffs after they won a National League Wild Card tiebreaker over the Giants. The team lost to the Braves in the NL Division Series, 3-0.