Kris Jenner's mom, Mary Jo Campbell, better known as MJ, died of acute cardiopulmonary arrest ... according to her death certificate.

A copy of the certificate, obtained by Us Weekly, revealed that acute respiratory failure and metastatic lung cancer also contributed to her death.

According to the certificate, MJ had been fighting lung cancer for months before she passed ... but it's unclear when exactly she was diagnosed.

Kris' mom had previously survived both breast and colon cancer ... but Kim Kardashian once shared on 'KUWTK' that the radiation from her treatment had caused intestinal damage.

The death certificate confirmed MJ died at an L.A. hospital on July 16 and was cremated on July 23. It also revealed no autopsy was performed after she passed.

Kris first announced her mother's death on Instagram with a touching tribute. She and her famous family held a 3-hour celebration of life at the La Valencia Hotel in San Diego Sunday, on what would've been her 92nd birthday.