Cincinnati's Spring Training roster now has 59 players.
Bernadina, 29, split the 2013 season with the Nationals and Phillies and batted .181 in 112 games. Washington released him on Aug. 19, and he was picked up by Philadelphia two days later.
The decline in production came after a strong 2012 season for the Nationals, when Bernadina batted .291/.372/.405 in 129 games, with five home runs, 25 RBIs and 15 steals.
Bernadina, who bats and throws left-handed and can play all three outfield positions, could provide added depth in center field behind rookie Billy Hamilton. Cincinnati is planning on going with Hamilton as its leadoff hitter as well, following the departure of free agent Shin-Soo Choo.
However, the Reds have been looking for a veteran outfielder for protection and to possibly alleviate some pressure off Hamilton. The club nearly had a deal with free-agent center fielder Grady Sizemore last week before he changed his mind and signed with the Red Sox.
Over his six big league seasons, Bernadina is a lifetime .239/.307/.359 hitter. His style of making tough catches in the outfield earned Washington fans' respect and the unique nickname of "The Shark," which also spawned a "Sharkadina" fan blog. He has some history with the Reds' Triple-A Louisville manager, Jim Riggleman, who was Bernadina's skipper for the Nationals from 2009-11.
A native of Curacao who now lives in the Netherlands outside of Amsterdam, Bernadina was originally signed by the Nats' franchise in 2001 when it was the Montreal Expos. Before his release by the Nationals, he was the longest-tenured player on the team.
As Spring Training opens on Feb. 14, Cincinnati has been making bargain deals with free agents seeking jobs.
On Monday, the Reds signed former Rockies infielder Chris Nelson, and on Wednesday, ex-Tigers infielder Ramon Santiago was signed to potentially be a backup shortstop. Like Bernadina, both players were signed to Minor League contracts and invited to big league camp.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.