Amid emotional scenes at the High Court in Auckland, Mr Kahui was found not guilty of the murder of Chris and Cru and not guilty of manslaughter.
The jury started deliberating after lunch today and returned less than 15 minutes later, after a trial which lasted six weeks.
The crown said the twins were fatally injured on June 12, 2006, and were admitted to Middlemore Hospital the next day, dying five days later at Auckland's Starship Children's Hospital.
They had severe brain injuries, broken ribs and Chris had a broken leg.
Mr Kahui was charged in October 2006, after a high profile police investigation.
As the foreman read the jury's verdicts to the packed public gallery Mr Kahui remained composed but fought back tears and looked toward the ceiling.
Family members and supporters, including his parents and siblings in the public gallery, let out an audible sigh of relief after the first not guilty verdict.
The twins' mother, Macsyna King, was not in court but her brother, Stuart King, the partner of Mr Kahui's sister Mona, was.
Mr Kahui's family wept openly and hugged as the second not guilty verdict was read out but composed themselves when Justice Geoffrey Venning asked the jury what their verdict on the manslaughter charges was.
When the final not guilty verdicts were given, family members wept and hugged each other, visibly relieved.
As Mr Kahui looked overwhelmed his defence lawyers Lorraine Smith and Michele Wilkinson-Smith hugged and also fought back tears, hugging Mr Kahui.
While Mr Kahui was taken from the court to be released, family members remained in the public gallery in a circle, holding hands and praying.
Minutes later, Mr Kahui walked out of the court to a huge media scrum.
When asked how he was feeling Mr Kahui replied, "Good, real good."
Flanked by his family and his lawyers Mr Kahui, whom Mrs Smith had described in court as inarticulate, was clearly overwhelmed by the large media presence and at a loss for words.
When asked what his plans were, Mr Kahui said he wanted to "try to start my life again".
Mr Kahui was asked what he meant but could not respond amid all the attention from the cameras and reporters.
Mrs Wilkinson-Smith came to Mr Kahui's aid, saying he was not able to think about what that meant.
After one reporter asked Mr Kahui who did hurt his babies his lawyers interrupted and said he could not answer that question and said he would not answer any more.
Mrs Smith said she was delighted with the verdict.
"But we must never forget that two babies have died.
"This is what the system is all about and the system has worked."
A family spokesman read a statement outside the court to the media.
"Right now Chris and his whanau want to gather themselves together and regroup as a whanau after an extremely difficult two and a half years.
"They have asked that everyone just gives them a chance to regroup and they will choose someone from the media to tell their stories to at a later date.
"Chris continues to express his innocence in the deaths of baby Cru and baby Chris and is pleased he has been eliminated as a suspect."
The family understood this was not a time to celebrate because the blood of two babies still cries from the grave for justice, he said.
"It's their prayers that this justice will be seen and be done."
The officer in charge of the case, Detective Inspector John Tims, told media outside the court he respected the jury's verdict.
"It is disappointing. We still have two twins, Cru and Chris, who no-one's been made accountable for their deaths."
