Per club policy, terms of the deal were not disclosed. The Royals will announce a corresponding roster move at a later time.
Volquez, 31, enjoyed a career year in 2014 with Pittsburgh, going 13-7 with a 3.04 ERA (65 ER in 192.2 IP), holding opposing hitters to a .235 batting average.
His ERA ranked 15th among qualifying National League starting pitchers, while his 7.75 hits allowed per nine innings ranked eighth among the league's starters.
Volquez will begin his 11th Major League season in 2015, after debuting for the Texas Rangers in 2005. The righty is 66-59 with a 4.44 career ERA, holding opponents to a .252 batting average. He was a National League All-Star and finished fourth in the league's Rookie of the Year voting in 2008 with Cincinnati, posting a career high 17 wins, going 17-6 with a 3.21 ERA and 206 strikeouts in 196.0 innings.
He was originally signed by Texas as an undrafted free agent in 2001. Along with the Rangers (2005-07) and Reds (2008-11), Volquez has also pitched for San Diego (2012-13) and Pittsburgh (2014). He has also pitched in the World Baseball Classic twice for the Dominican Republic, helping them win the tournament in 2013.
A native of Barahona, Dominican Republic, Volquez resides in Santo Domingo during the offseason with his wife, Roandy and twin daughters, Eylin and Aylin, who were born November 5, 2013.