The 25-year-old will fly to Valencia to undergo a medical and will be officially presented to the media on Friday, the paper said.
Joaquin was consistently linked with a host of clubs during the past year but Valencia looked to have won the race for the skillful winger's signature.
He claimed earlier last week that he would like to part ways with Betis for a new challenge, although his contract runs out in 2010.
"I have spoken with (coach Javier) Irureta and told him that it is time for me to leave," Joaquin was quoted as saying by AS newspaper.
"I've achieved everything possible at Betis and now I want to continue my career at another club."
Joaquin came through the youth ranks at Betis, scoring 29 goals in 181 appearances and helping his team win the Spanish cup in 2005.
The Spanish international will be Valencia's fourth signing in the off-season after acquiring the services of Chelsea defender Asier Del Horno, Liverpool striker Fernando Morientes and Empoli's Francesco Tavano.