Getty Images SportLewandowski scored twice either side of half-time to give Barca a morale-boosting win, and Cubarsi looked at home in the heart of the backline.
Hansi Flick will have been keen for his side to lay down a marker in their opening La Liga game and while that didn't quite happen, Barca did manage to start their campaign with a victory.
Barcelona huffed and puffed throughout the first half and went into the break 1-0 down, thanks to some slick Valencia interplay.
A brilliant cross from Diego Lopez, who beat Jules Kounde with a great stepover, was met at the back post by Hugo Duro, who headed home. A VAR review confirmed that he was onside.
And Duro almost had a second just two minutes later, as he beat Marc-Andre ter Stegen from close-range but was denied by a superb sliding Pau Cubarsi block.
The block proved vital, as Barcelona were able to equalise in added time of the first period. Lamine Yamal got on the end of an Alejandro Balde cross and played the ball across goal, with Robert Lewandowski able to finish.
After the restart, Raphinha won a penalty after being fouled in the box, and Lewandowski stepped up to score his second goal of the night.
Valencia faded badly thereafter, as Barca were able to see out what ended up as a comfortable win.
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