Searchers scoured more than 130 miles of coastline looking for Randall Young, 51, of Morro Bay, who was last heard from on April 28.
A friend who reported him missing said Young had gone camping alone with a kayak at the Plaskett Creek campground in Big Sur and was supposed to return on Sunday.
Young failed to return, and when the friend went to check on him, she found his car at the campsite but no sign of him or his belongings, according to the Coast Guard.
An 87-foot Coast Guard patrol boat and helicopter were used to search the water, while sheriff's deputies looked for Young on land.
A camper reported seeing a white, 12-foot kayak somewhere along the shoreline on Monday afternoon. It has not been determined whether the kayak belonged to Young, Richards said.
Young is described as a white male, 6 feet 3 inches tall with a medium build.
Anyone with information about his whereabouts is asked to call the Monterey County Sheriff's Office at (831) 647-7702 or the Coast Guard at (510) 437-3701.