The Nationals recalled Dion from Triple-A Rochester on Tuesday, Spencer Nusbaum of The Athletic reports.
Dion was part of a collection of players acquired from the Guardians in Monday's Foster Griffin trade, and he will take Griffin's vacated roster spot. The lefty reliever holds a 4.58 ERA but a promising 25:3 K:BB over 19.2 innings across 12 appearances at the major-league level.