The 25-year-old Moore, who hit 31 home runs each of the last two years in the minors, already has six home runs and 16 RBI through 20 Triple-A games this season.
One-time second baseman Mark DeRosa, who has played exclusively in the four corner positions for the Nats this year, heads to the disabled list with an as of yet undisclosed injury.
Though most of his minor league experience is at first base, Moore played several games in the outfield this spring and will likely split his time with Xavier Nady, Roger Bernadina and Jayson Werth at the corner outfield spots.
While Moore has put up gaudy power numbers in the minors, he has shown little to no plate discipline. He holds a career .319 OBP and has struck out in over 23 percent of his professional plate appearances.