Giffords arrived in the dining hall at Davis-Monthan Air Force Base at midday Thursday wearing a ball cap and an apron with her nickname of "Gabby" sewn on the front. She was accompanied by her retired astronaut husband, Mark Kelly, who also donned an apron.
Giffords used only her left hand as she served, a sign that physical damage remains from the injuries she suffered when she was shot in January.
Kelly supported her from her left side as she worked the turkey station on the serving line. He served ham.
Afterward, she mingled with service members, exchanging pleasantries and mostly one word greetings and responses.
She did tell Airman 1st Class Millie Gray, of Kansas City, Mo., "Happy Thanksgiving, thank you for your service."
Gray said she had intended to only grab a plate and head back to her dorm to eat, until she heard that Giffords was going to be there.
"She's such an inspiration and her story is so inspirational, it really made me proud. I felt very proud and very humble," Gray said. "It just feels really good to see that she is out here supporting the troops, and just continuing to be an inspiration and a strong role model for Americans in general.
"She was very warm, asked how our meal was, which, of course, was amazing. The food is awesome," Gray said. "She and her husband were very, just delightful and asked a lot of questions. It was just very warm-hearted, and I told her she was an inspiration and she was very thankful for that."
Giffords and Kelly left after less than an hour.
Giffords has been undergoing intensive rehabilitation at TIRR Memorial Hermann in Houston as she recovers from a gunshot wound to the head. She was among 19 people shot Jan. 8 as she met with constituents outside a Tucson supermarket. Six people died.
The congresswoman arrived in Tucson on Tuesday evening from Houston for a private visit with her parents and other family members and friends.
"It's always special to have a member of Congress come and spend time with the troops and show support," said Brig Gen Jon Norman, acting commander of the Acting commander of the 12th Air Forces, Southern. "But after everything that she's been through, it's a little bit more special."
Giffords' staff said base officials originally asked a member of the congresswoman's staff to take part in the annual Thanksgiving dinner. When the staff member told Giffords about the event, the congresswoman decided she wanted to go herself.