Maria Louise Hopes, 46, and her son Leon Port, 24, were jointly accused of murdering Mark Hopes, 45, at the couple's home in Trealaw last October.
They blamed each other for the killing, Merthyr Tydfil Crown Court heard.
Port was previously found guilty of Mr Hopes's murder, but there was a retrial after the jury could not reach a verdict on his mother.
Both mother and son admitted perverting the course of justice, along with Port's girlfriend Rebecca Donovan, 24.
All three will be sentenced at a later date.
The court heard the violence began with an argument between Mr Hopes and Port on the afternoon of 2 October, which ended with Port throwing punches.
Port, of Mountain Ash, claimed that was the end of his involvement and said his mother pulled her husband from the sofa and hit him with a weapon, causing the fatal injuries.
Hopes claimed her clothing was covered in blood because she helped clean her husband up, but the jury heard attempts were made to dispose of the evidence, with blood found on a mop and on an outside drain cover.
It was not until the following day that Port called 999 and tried to deflect the blame from himself. He told the operator Mr Hopes had been out drinking and had come home injured.
Prosecuting, Christopher Quinlan said Mr Hopes suffered "significant external and internal injuries" to his head, face and body.
"He was beaten to death in an assault which must have lasted an appreciable time and involved the use of a weapon," he added.
Mr Quinlan said Hopes and Port had "helped themselves and each other and not the dying Mr Hopes."
A Rhondda Cynon Taff  woman has been found guilty of murdering her husband after trying to blame it on her son.