The Nationals announced the move before Wednesday night's game at San Francisco. Manager Matt Williams says an MRI on Ramos revealed a Grade-1 hamstring strain.
Williams hopes Ramos will be back in the lineup as soon as he's eligible to come off the DL.
Ramos was injured running out a double in the ninth inning of Tuesday night's 2-1 win against the Giants. He was taken out of the game and initially thought the injury wouldn't sideline him.
Ramos is batting .261 with one home run and 11 RBIs. Jose Lobaton started at catcher Wednesday night.