The reunited couple held hands for two hours, said Giffords spokesman C.J. Karamargin.
"It was actually a very touching moment," Karamargin said Thursday evening. "They are smiling ear-to-ear and haven't let go of each other's hands."
Kelly had rushed to Giffords' rehabilitation center after a public celebration that lasted more than an hour for the six-man Endeavour crew's return home to Houston. He caught Giffords still putting on her makeup, Karamargin said.
Giffords, who was shot in the head during a mass shooting in Tucson, Ariz. in January, changed from sweats to jeans and a blouse. She had already eaten so it wasn't a dinner date, but that didn't matter.
It had been 18 days since they had last been together, right before Endeavour's May 16 launch. Then Endeavour blasted off, traveling to the International Space Station. Endeavour landed Wednesday and the astronauts returned to Houston's Ellington Field where hundreds of people cheered them on.
It was an emotional curtain call for the next-to-last shuttle flight, with the astronauts signing autographs after each talked about the support from co-workers and family.
While the crew singled out individual workers and departments at Johnson Space Center, they emphasized the sacrifices of their loved ones.
"I want to thank my family -- Gabby who is not here today -- Claudia and Claire who are here in the front row," Kelly said, referring to his wife and daughters. "I could not do it without their support."
Endeavour astronaut Drew Feustel added a special note to his wife, Indira: "Honey, happy anniversary today."
And the astronauts also praised the ship that will no longer be flying. After 19 years and 25 flights, "Endeavour performed as if it was brand new," Kelly said.
"It's not the end of Endeavour either," Kelly said. He said Endeavour will continue to inspire young people to study science and engineering at its new post at a Los Angeles museum.
And future spaceships will learn from the space shuttle fleet, which is retiring after the scheduled July 8 launch of Atlantis, said Endeavour astronaut Roberto Vittori.
Kelly called Giffords almost daily via telephone, and had one video hookup during the mission, Karamargin said.
Giffords left rehab in Houston to be at Endeavour's May launch. Johnson Space Center Director Mike Coats, a former astronaut, praised Kelly for the way he compartmentalizes family and NASA duties, like most astronauts: "He's probably had a bigger challenge than most. He did a terrific job."