The 27-year-old, previously voted The Sun's sexiest man, revealed it was the first time he had done it, saying he agreed because it was for an old friend, reported Sun Online.
"It's a very private, lovely thing to be asked to do. Of course I'm going to make a joke after it if it goes well - 'I do weddings. Next will be children's parties and bat mitzvahs. It's a mainly Jewish and gay audience so hopefully they will be lenient towards me," he said.
"The hotel was lush, the bridegrooms were beautiful, and the man who married them to each other was Benedict Cumberbatch - so yes, it was quite a blast," said the guest.
Benedict arrived in Ibiza on Friday, his 37th birthday, after finding out he had been nominated for an Emmy for his role in the BBC's 'Parade's End'.