Hill, 34, has played in parts of 10 big league seasons, seeing time with the Dodgers, Diamondbacks, Cubs and Marlins. He appeared in 18 games with Miami last season, hitting .155 with a .373 OPS in 58 at-bats.
A career .206 hitter, Hill had his best big league season in 2009, when he posted a .636 OPS in 83 games with the Cubs. He's viewed as a solid defensive backstop.
This isn't the first time Hill has spent time in the Nationals organization; he played in 31 games with Triple-A Syracuse in 2012.
Hill is the seventh catcher that the Nats have invited to big league spring training, joining Wilson Ramos, Jhonatan Solano, Sandy Leon, Chris Snyder, Brian Jeroloman and Jeff Howell.
Solano, Leon, Snyder and Hill will compete to be Ramos' backup. The latter two were both signed as minor league free agents this offseason.