The deal includes a fourth-year club option that could bring the overall value to more than $20 million. It follows Arizona's multiyear contracts with players such as center fielder Chris Young and pitcher Dan Haren, infielder Chad Tracy and outfielder Eric Byrnes.
"As we have with a few other guys, to lock in a core player, fix the prices but also buy out a year or two of free agency, that allows us to keep our core together," general manager Josh Byrnes said in a conference call Tuesday.
Snyder has four years of major league service, so Arizona is buying out two years of salary arbitration and his first year of free agency with the three guaranteed years. If the Diamondbacks exercise their club option for 2012, they'll buy out a second year of free agency as well.
Snyder, also speaking on a conference call, said he is happy to know he'll be with the club for the long term. He could give up two free agency seasons if the option is picked up.
"It's a young core," the 27-year-old Snyder said. "If we stay together, definitely we'll be contending in the National League West, if not further than that."
Snyder, 27, was Arizona's second-round pick in the 2002 first-year player draft. He's a .238 hitter with 46 home runs in five seasons as a Diamondback. Last year Snyder put up his best career power numbers, hitting 16 homers and driving in 64 runs in 115 games. The homers were a record for a Diamondbacks catcher.
Snyder did not commit an error in 847 total chances. He has one error in 1,629 chances in the last two seasons for a .999 fielding percentage.
"He handles the defensive side and the intangible side of the position very well," Byrnes said. "It's sort of immeasurable what he does as far as preparing for an opponent, working with the pitchers, the toughness that he brings."
Jerry Crasnick covers Major League Baseball for ESPN.com. Information from The Associated Press was used in this report.