Emergency services said that 29 people were rushed to hospital after the collapse in the coastal province of KwaZulu-Natal.
Local officials have blamed the tragedy on heavy rainfall in the area around eMpangeni on Thursday night.
Most of the victims were reportedly women sleeping in the church.
An 11-year-old girl is thought to be among them.
The wall at the front of the Pentecostal Holiness Church collapsed at the start of what had been planned as a weekend-long service to commemorate the Christian festival of Easter.