Ben Hooper, 38, was supposed to leave Africa's western coast from Dakar, Senegal last Tuesday but is stuck due to a problem with the support vessel.
"The electrician is still working on big blue so we will now be leaving Monday," Hooper wrote in a Facebook post, referring to the vessel.
Hooper is wrapping up three years of preparation for the immense journey that will see him swim up to 10 hours a day for nearly five months with the aim of reaching Brazil.
He will rack up 1,635 nautical miles, equal to nearly 1,900 land miles (3,000 kilometres) over the course of the journey, while taking in up to 12,000 calories a day.
Hooper's journey will be observed by a Guinness World Records representative who will join a crew of 10 supporting the swimmer.
His crossing will be filmed and can be tracked on his "Swim the Big Blue" website.
