The Catalans made a lethargic start and fell behind in the 16th minute when striker Joseba Llorente bundled the ball into the net but they salvaged a point when Ronaldinho equalised with a neat finish just before halftime.
Barca remained in second place in the table, level on 21 points with Villarreal and four behind leaders Real Madrid after 10 games.
"I'm not too worried because leagues are won in the second half of the season and we've still got a strong chance of winning the title," Barca coach Frank Rijkaard told reporters.
Atletico Madrid are fourth on 20 after their entertaining 4-3 win over Sevilla on Wednesday, three clear of Espanyol who were held to a 0-0 draw at home to Real Murcia on Thursday.
Valladolid's only victory this season came in their opening match against Espanyol but they made a confident start at the Zorrilla.
The lively Jonathan Sesma fired into the side-netting after outpacing Carles Puyol and fellow midfielder Sisi was only denied a goal by a fine diving save from Victor Valdes after unleashing a fierce drive from the edge of the area.
Barca failed to heed the early warnings, though, and went a goal down when Llorente bundled home after Sesma had found space down the right wing and curled a clever pass behind the back four.
The visitors struggled to respond and although they enjoyed plenty of possession they were frustrated by Valladolid's pressure play in midfield.
It was not until Xavi threaded a clever through ball into Ronaldinho's path three minutes before the break that they broke down the Valladolid defence.
The Brazilian, under fire for his below-par performances this season, evaded his marker and lifted the ball over diving keeper Alberto.
Barca almost took the lead 12 minutes into the second half, 17-year-old forward Bojan Krkic hitting the base of the post with a stinging shot after Lionel Messi had surged upfield.
But Valladolid kept their composure and twice went close to reclaiming the lead, Valdes blocking a point-blank header from Sesma and saving another fine shot from the midfielder.