Valencia, beaten by Werder Bremen in the Champions League in midweek, took the lead in the 10th minute when Marco Di Vaio shot low from the edge of the area but Betis equalised just past the half-hour mark when Edu converted a Ricardo Oliveira cross.
Di Vaio and fellow Italian Bernardo Corradi squandered the best chances late in a frustrating game for the champions, who will be disappointed at merely extending their unbeaten start to the season.
A draw was enough to give Valencia a one-point lead in the Primera Liga but Barcelona can climb two points clear at the top if they win at home to Numancia on Sunday. With six games played, Valencia lead with 14 points, followed by Barcelona with 13 points from five.
Atletico Madrid missed the chance to join Barca in joint-second place when they were beaten at Real Sociedad, who claimed their first win of the season thanks to a Darko Kovacevic header five minutes before the break.
Atletico drop to fifth place on 10 points from six games, while Sociedad move up from last place to 13th with five.
Real Madrid, in eighth place with nine points, host 14th-placed Deportivo Coruna on Sunday in a battle between two sides yet to
BRIGHT START
Valencia, missing in-form winger Vicente through injury, nevertheless made a bright start and Stefano Fiore and Miguel Angel Angulo both went close before Di Vaio cut inside and beat Toni Prats with a low shot inside the keeper's right-hand post.
Betis were struggling to get the ball off Valencia's talented midfielders but they almost snatched an equaliser in the 20th minute when Edu flashed a shot across goal.
Joaquin then gave Valencia a scare with a dangerous cross from the left and in the 31st minute Betis grabbed the equaliser.
Ruben Baraja, otherwise faultless in midfield, lost the ball and Oliveira took the chance to race clear down the left and cross for the unmarked Edu to turn in at the far post.
Betis enjoyed a good spell either side of halftime but Valencia finished more strongly and had ample opportunity to take all three points.
With 15 minutes to go, Corradi launched a quick break out of defence and in a flash Di Vaio was set clear on goal only to see a weak shot blocked by Prats.
Corradi was then guilty of two bad misses himself, flicking a brilliant Xisco cross into the side-netting with a couple of minutes to go and then heading well over when another cross from the right had given him a clear chance for the winner.