Reid Stowe, 58, docked in Manhattan after his 1,152 day voyage, and was greeted by his girlfriend and 23-month toddler who he had never seen.
Mr Stowe left in the 70-foot (21m) two-masted sailing boat in April 2007.
Guinness World Records say they are looking into the claim that the trip sets a new record for the longest voyage.
Mr Stowe originally set off with his girlfriend, Soanya Ahmad, 26, until she had to return to shore after suspecting she was pregnant.
The couple agreed that he would continue without her, despite it meaning that he would miss the birth of their son.
He said that seeing her go was the hardest part of his trip.
"Before we left, we had an agreement that if I had to get off for any reason, he would go on," Ms Ahmad said.
"I knew if he came back and didn't finish the voyage, he would just go back again. There was no way he wasn't going to finish it."
The vessel was built by Mr Stowe and his family 30 years ago, and named "Anne" after his mother.
While at sea, Mr Stowe says he spent his time repairing torn sails, painting, practicing yoga and writing a book.
He was able to send e-mails and make satellite phone calls.
Mr Stowe refers to his trip as a "voyage of love".
"She's done what no vessel in the world has done," Mr Stowe said.
"She got worn out and beat down to death.
"I'll tell you that boat will take me for another year and there is still a years worth of food on that boat...It's a magical boat, it's full of love."
Charles Doane, editor of Sail magazine, said he believes that Mr Stowe set a new sailing record.
He said that the GPS satellite system that tracked the voyage provides evidence that the boat had not touched land during the trip.