Diego Alves' penalty save from the Argentine denies Catalans from taking a lead back to Camp Nou but Pep Guardiola will still be confident of overcoming Los Che in the return leg
The hosts deservedly led through Jonas' emphatic finish midway through the first period, only for Puyol to level the match before the break with his downward header.
A subdued opening found life when Messi embarked on a typically dangerous run, drawing a free kick, but the Argentine's effort lacked sufficient curl as it went a yard off target.
With Los Che beginning to dominate proceedings, the Mestalla were left infuriated when Jose Pinto prevented Roberto Soldado from putting Unai Emery's side ahead when he clearly handled outside the area. The officials were disinterested in Valencia's claim as play continued. much to the amazement of the Spain striker.
Valencia continued their high intensity and were soon rewarded when they dispossessed Barcelona deep in their territory. They worked the ball out to Jeremy Mathieu whose cutback was expertly converted by Jonas for the lead.
Suddenly, Barca found a rhythm. Isaac Cuenca's sublime foot work was followed by an intricate ball into the feet of Alexis. The Chilean managed to dig out a shot only to be denied by a brilliant save from the onrushing Diego Alves.
From the resulting corner, the Blaugrana opted for a customary cross which brought dividends when an unmarked Puyol brought the scores level with a committed header.
Messi began the second half brightly, and had a wonderful chance to fire Barcelona ahead after Thiago had been felled in the penalty area by Miguel's flailing leg. The Argentine's fragmented run-up did nothing to deter Diego Alves, who pushed his poor spot kick away to safety after springing low to his left.
Barca continued to provided attacking intent but Diego Alves continued his heroics when he palmed Eric Abidal's audacious effort around the post. The Brazilian stopper was then fortunate to see Gerard Pique's header from the resultant corner miss the target.
Pep Guardiola introduced Dani Alves in search of a winning goal and the Brazilian came close to providing it when he combined with Messi. The South American duo played a delicate one-two, with Alves hammering the return pass against the upright before Valencia desperately cleared.
As the match drew to a close neither side lamented any late misses as each began to prepare mentally for the return leg. Guardiola's side will be confident of securing a third Copa del Rey final in four years following Puyol's priceless away goal, although Los Che will still believe that they can progress.