Dozens more were injured when the 13-foot (four-metre) high concrete wall collapsed, trapping guests who had taken shelter from violent rain in a tin shack on Wednesday night, Indian police superintendent Anil Tank told AFP.
“We worked through the night,” one rescue worker at the scene in Bharatpur, Rajasthan state, told India TV news network.
“We tried to rescue as many people as possible, the scene was horrific.”
Tank, a senior officer in Bharatpur, said 26 people were injured, 15 of them seriously. Television footage showed anxious relatives standing next to hospital beds.
Police have launched an investigation and detained a wedding hall manager on charges of causing death by negligence.
“We have registered a case and taken one of the managers of the banquet hall into custody,” district magistrate Narendra Kumar Gupta told reporters.
“We will investigate if the hall owners had a valid licence. In case they did not have a licence, appropriate action will be taken against them.”
Gupta also announced compensation of 50,000 rupees ($775) for the family of each person killed.
Prime Minister Narendra Modi said the incident had pained him “beyond words”.
“My thoughts are with the families of the deceased. I hope the injured recover soon,” he tweeted.
Indian weddings are often grandiose affairs with huge numbers of guests and lavish ceremonies that run for several days.