Wildlife officers are heading to waters off Sydney's North Head to help an entangled whale calf.


The calf and its mother, believed to be humpbacks, were seen leaving Sydney Harbour on Thursday afternoon heading northeast, a National Parks and Wildlife (NPWS) officer said.


"It looks like the calf has got an entanglement of some sort," he told AAP.


The whales were under observation and an NPWS crew was heading out by boat to assess if it was safe to try to disentangle the calf, he said.


The whales were moving at about three to four knots which was typical behaviour and the entanglement did not seem to be slowing the calf down too much, the spokesman said.


A spokeswoman for the Sydney whale watch group Orcas said a keen member had spotted the pair off the eastern suburbs near the Macquarie lighthouse and called the Orcas hotline.


The NPWS had then been alerted.


"We've got a whole lot of rope and three buoys that it's dragging," the spokeswoman told Macquarie Radio.


AAP