Ramos was signed by the Minnesota Twins as a non-drafted free agent on July 7, 2004. He caught 43% of potential base stealers in his minor league career, and has a .987 fielding percentage. In 2008, with the Twins' High-A affiliate, the Fort Myers Miracle, he batted .242 with eight home runs and 42 runs batted in in the first half of the 2008 season, helping his team capture the Florida State League first-half West Division title. When 2008 Florida State League All-Star catcher James Skelton of the Lakeland Flying Tigers suffered an injury, Ramos was added to the West Division All-Star team, joining teammates Robert Delaney, Brian Dinkelman, Jeff Manship, Anthony Slama and Danny Valencia.
Ramos' batting average jumped to .333 in the second half of 2008. For the season, he batted .288 with thirteen home runs, and was named to the All FSL Team. His 78 RBIs was fourth in the Florida State League.
Ramos entered the 2009 season ranked as the Twins third best prospect by Baseball America behind Aaron Hicks and Ben Revere, and #71 in all of minor league baseball. The Twins added Ramos to their 40-man roster, and invited him to Spring training. After which, he was assigned to the Twins' double A Eastern League affiliate, the New Britain Rock Cats. He broke his right index finger in May and suffered a hamstring injury in June, forcing him to do a nearly two-month rehab assignment, during which he hit three home runs in five games with the Gulf Coast League Twins. Ramos rejoined his team in August, and batted .317 with four home runs and 29 RBIs for the season.
Ramos batted over .400 in spring training in 2010. However, with Joe Mauer behind the plate, the Twins sent Ramos to the Triple-A Rochester Red Wings rather than have him serve in a back-up role in the majors.
Ramos received his first major league call-up on May 1, when Mauer was sidelined by a bruised left heel and was limited to emergency pinch hitting. Ramos took the roster spot of Pat Neshek, who was placed on the 15-day disabled list retroactive to April 29 with inflammation of the middle finger on his right hand.