Nik Wallenda said he had planned to walk by himself across a 91m wire, but his mother convinced him to let her join him on the reconstruction of the fatal 1978 stunt.
"I've been mentally prepared my entire life for this," he said. "I've seen the video of my great-grandfather falling hundreds of times. It's something I've been wanting to do for all of us, for our family."
He said he initially rejected a request by his mother, Delilah Wallenda, to join him.
"Just because of safety," he said. "We've obviously lost several family members doing this."
But Delilah Wallenda, who is in her late 50s, eventually won him over, he said.
The mother-and-son team walked slowly toward each other on a damp morning, balancing on a wire. Nik Wallenda was wearing moccasin-style shoes that his mother had made. He carried a 20kg balancing pole, while Delilah Wallenda carried an 11kg pole.
They met at the middle. Delilah Wallenda sat on the wire while her son stepped over her in slow motion. She then struggled slightly to get up before both continued toward the towers of the Conrad San Juan Condado Plaza Hotel.
"Normally, I'm in a zone," he said. "At this point, I was in no zone. I was still focused on my great-grandfather."
Dozens of onlookers on balconies and the street below gasped as he knelt and steadied himself just metres before he completed the walk.
The Wallendas obtained permission to do the stunt about two months ago so they could commemorate German-born Karl Wallenda, who was 73 when he fell to his death after a lifetime of spectacular acrobatics. He was the founder of the "The Flying Wallendas" high-wire act.
In 2001, another relative, Tino Wallenda, crossed a 91m cable at a prison in Puerto Rico and did a headstand in honor of Karl Wallenda.
Nik Wallenda said Saturday's walk was an emotional experience.
"It was to show the world that the Wallendas are still here, we're still going strong," he said. "My great-grandfather always said, 'Never give up,' and that's something we'll never do."
