HM Coastguard said a search operation is being carried out after the man failed to surface while diving two miles out to sea.
The Coastguard helicopter is searching along with the Whitby RNLI Lifeboat and Scarborough inshore and all weather RNLI lifeboats.
Three HM Coastguard rescue teams from Whitby, Burniston and Ravenscar are also involved in the search.
A HM Coastguard spokeswoman, said: "HM Coastguard is currently coordinating a search for a diver who has failed to surface off the coast of Scarborough. The man was diving two miles off the North Yorkshire coast."