The 27-year old Johnson hit .289 with 35 doubles, 15 home runs and 74 RBI in 131 games for the Nationals in 2005. His team-leading .408 on-base percentage ranked sixth in the National League.
"We are very pleased to be able to lock up Nick Johnson, who we view as one of the core players who will take the Nationals to the next level," said Nationals vice president and general manager Jim Bowden. "Nick is a complete player both offensively and defensively, and we appreciate his positive influence in the clubhouse. He is the type of player and person that the Washington Nationals are all about."
The slick fielding Johnson also amassed a .996 fielding percentage, third best among National League first basemen.
Johnson is a .265 career hitter with 53 home runs and 220 RBI in 452 big league games with Washington/Montreal and the New York Yankees