On 3 December 2015, Fanning claimed his first World Qualification Series (WQS) victory in Hawaiian surf by winning the 2015 Vans World Cup at Sunset Beach, Oahu.
On 19 July 2015, Fanning encountered a shark two minutes into the J-Bay Open 2015 finals at Jeffreys Bay, South Africa. Fanning was in the water with Julian Wilson during the final when what was suspected to be a great white shark swam next to him. Fanning punched the shark and tried to wedge his board between the shark and his body. The shark eventually bit off Fanning's leash and Fanning started his attempt to flee back to shore. Wilson paddled towards Fanning to assist him and was praised for his action and hailed as a hero. Much of the early coverage characterized the encounter as a "shark attack." Based on analysis of the video and the fact that Fanning was not bitten, some marine biologists believe the shark had no intention of biting him. However, as there was physical contact between the shark and his board and the shark cut the leash, the International Shark Attack File has classified the encounter as a shark attack.
The next day, Fanning returned to Australia. He wondered why the shark did not bite him and told reporters: "I'm just lucky it wasn't my time." The story received international news coverage. Fanning returned to the water to surf again less than a week later, dedicating it to his late brother, and also surfed Ship Stern Bluff on 27 August, a break notorious for great white sharks. Fanning later competed in the Billabong Pro Teahupoo, which took place in August 2015 in Tahiti. Fanning would go on to take a victory at the Hurley Pro at Trestles Beach and finish the year 2nd in the ratings.