A seven-year-old boy has died after being found unconscious at the bottom of a swimming hole west of Sydney.

The child's parents called emergency services to Jellybean Pool in the Blue Mountains National Park at Glenbrook at 2:25pm, saying he had been missing for almost 30 minutes.

Police said family members pulled the boy from the water at 2:45pm and officers from Blue Mountains Police Area Command, the Dog Unit and Rescue Squad performed CPR.

NSW ambulance paramedics then took over and a rescue helicopter winched a medical team to the scene.

The child was taken to the Nepean Hospital but police said he died shortly after arrival.

A report will be prepared for the coroner.