Speaking after the annoucement Guerra said
"I am very thankful for the warm welcome I have received here at Cardiff City and am very excited for my new challenge in Wales.
"Hopefully I can keep up the level that I have been playing at in Spain for the last few seasons and that it will be a successful time for me in Cardiff, with both the club and the supporters."
The 32 year old scored 72 goals in 149 games for Valladolid since joining them in 2010.
He started his career with Barcelona-based Espanyol before joining La Liga giants Valencia in 2004, where he developed at the Mestalla's B team.
Guerra has played for Granada, Mallorca, Alaves and Levante before he joined Valladolid in 2010, where his goals helped them to the La Liga promotion play-offs in 2011.