Villarreal sign Dos Santos from Mallorca
"I am delighted to take this next step in my career, and finally to be able to play for Villarreal, a great club I was about to join last year before they were regrettably relegated," Dos Santos was quoted as saying on the Villarreal website.
The 24-year-old former Barcelona and Tottenham Hotspur player had a loan spell with Racing Santander in the 2011/12 campaign when he worked with current Villarreal coach Marcelino Garcia Toral.
Dos Santos, who came up through the Barca youth ranks and debuted with the first team aged only 17, has scored 14 goals in 67 international appearances with Mexico.
Villarreal, Champions League semi-finalists in 2006, won promotion back to La Liga last month after one season in the second division.