Andy Carroll netted his third goal of the summer by capitalising on a mistake by David Albelda in the sixth minute, the striker picking up the ball, hitting it against the post off goalkeeper Diego Alves and finishing at the second attempt.
The hosts then made it 2-0 in the final minute of normal time thanks to a goal which was announced as Dirk Kuyt's, even though replays suggested Sotirios Kyrgiakos had got the last touch.
The game proved to be a comfortable workout for the Reds ahead of their Barclays Premier League opener against Sunderland next Saturday and manager Kenny Dalglish - who had seen his side ship 15 goals in their previous five friendly matches - will take encouragement from the fact that they did not concede.
Dalglish made only two changes to the starting line-up from Monday's 3-3 draw with Valerenga in Oslo, with former Valencia man Fabio Aurelio - featuring for the first time in pre-season - and Alberto Aquilani coming into the team.
Jack Robinson and Kuyt dropped to the bench, where they were joined by Lucas Leiva, who had returned to training with the Reds earlier in the week following his participation for Brazil in the Copa America.
Juan Mata, a reported target for several Premier League clubs over the summer, was included in the visitors' first XI.
Liverpool made a positive start and had the lead when an error by Valencia captain Albelda allowed Carroll to pounce.
Making a hash of a back-pass, Albelda played the ball straight into the path of the England international, who saw his initial shot through Alves' legs come back off the post but was alert enough to tuck away the rebound.
Moments later Dalglish was forced to make a substitution, Glen Johnson picking up an apparent calf problem and coming off for Martin Kelly.
Valencia then enjoyed a spell of pressure before Jordan Henderson drilled an effort wide for the hosts.
Another defensive lapse by the Spanish side let Carroll in again, but the 22-year-old could only shoot at Alves.
Carroll then received a yellow card after lunging in late on Adil Rami and getting into a skirmish with the Frenchman, before being on the end of a hefty challenge himself, Albelda flying in and also getting booked.
Lucas and Robinson were introduced at the break for Jay Spearing and Aurelio and soon after the restart Dalglish made four more changes, David Ngog, Maxi Rodriguez, Kuyt and Joe Cole coming on for Carroll, Stewart Downing, Henderson and Aquilani.
The substitutes were quickly into the action as Ngog shot wide from Rodriguez's tee-up.
Daniel Agger then lashed an effort over the bar, and Kelly struck a low drive towards goal which Alves dived to smother.
Kyrgiakos and John Flanagan entered the fray to replace Agger and Adam, and Tino Costa sent a free-kick over the bar for the away side.
Valencia substitutes Sofiane Feghouli and Roberto Soldado looked like they might threaten late on, but Liverpool wrapped up the win in the 90th minute, Kyrgiakos and Kuyt seemingly bundling the ball in between them from close range.
Dalglish admitted after the match that the shutout at the back was just as important as the goals scored.
"I think the boys deserve great credit for the work they have done out there," Dalglish said.
"I think they have got their reward for the hard work they have done in training by not losing any goals, and that is as pleasing for us as it is to score two at the other end.
"We are delighted with everyone's attitude and commitment, and for us to go and win against a very good side will not do us any harm."
In the remaining days before the Sunderland game, Dalglish will be welcoming striker Luis Suarez - who helped Uruguay win the Copa America - back to training and crossing his fingers that his players get through the midweek international fixtures unscathed.
"We have still got Luis to come back in so we will see how he is - he should be back in Monday or Tuesday I think," Dalglish said.
"Lucas has been back a week and it has been great to see him back and play 45 minutes.
"We are where we would like to be with most of them. We could have done without midweek internationals, but we just have to live with that and hope that no-one comes back injured."
Dalglish revealed that Johnson had in fact injured his thigh and would be assessed on Sunday.
Carroll, meanwhile, looks to be shaping up well.
"We were absolutely delighted with Andy's performance," Dalglish said.
"You can see he has gotten over his injury problems - he was flying about out there, which is great for us."