Gallardo free-kick rescues River in Superclasico
After the traditional ticker-tape reception, a scrappy first half at the Bombonera produced only a few chances.
Boca midfielder Sebastian Battaglia went close with a deflected shot and Rodrigo Palacios had a goalbound header stopped by goalkeeper Daniel Vega following an explosive break out of defence by Osvaldo Gaitan.
The second half was delayed as toilet rolls and other objects were cleared off the field, Vega popping balloons in his penalty area before Boca ground staff eventually stepped in to help.
Defending champions Boca went ahead in the 59th minute with a 25-metre shot from 35-year-old forward Martin Palermo, their record goalscorer.
River substituted lethargic striker Cristian Fabbiani and, although the player known as The Ogre was clearly furious at the decision, the change brought new life to the team.
In the 69th minute, Diego Buonanotte was tripped by Battaglia and the 33-year-old former Argentina, Monaco, Paris St Germain and D.C. United forward Gallardo curled his free kick into the top left-hand corner.
The draw left River fifth with 16 points from 10 games in the Clausura championship and Boca in 13th place with 12.
Velez Sarsfield beat Arsenal 2-0 on Saturday to lead the table on 22 points, one ahead of Colon, who beat Independiente 1-0 on Friday.
Lanus moved level with Colon by beating Tigre 2-1 in an evening game.
Norberto Paparatto gave Tigre a first-half lead but Maxi Velasquez rifled in the equalised three minutes later and Eduardo Salvio scored the winner in the 63rd minute after a weaving run by Jose Sand.
San Lorenzo, knocked out of the Libertadores Cup 10 days ago, continued their unhappy run with a 3-0 defeat at San Martin-Tucuman which left them 18th with 10 points.