UPDATE: Toddler dead after being pulled unconscious from NSW pool

A three-year-old boy has died after being found unconscious in a swimming pool at his home in Sydney's northwest.

Parents worked to revive the three-year-old boy, who was found floating in the pool at his Stanhope Gardens home this morning.

CareFlight's trauma team arrived shortly after 10am and paramedics airlifted the boy to The Children's Hospital at Westmead.

He could not be revived and was pronounced dead soon after arrival at Westmead.

Police investigations are continuing.

"As we go into summer it's an early reminder about the need for constant vigilance whenever young children and toddlers are near swimming pools, however secure they might seem," CareFlight spokesman Mark Lever said.