"He's still getting used to being free," Neller told reporters Tuesday.
Hekmati was detained since August 2011 after visiting Iran to see his dying grandmother. Iranian officials accused him of being a CIA spy.
"We talked about his being a Marine," Neller said. "He was an infantry Marine in combat so and he told me without me even asking that his training and his pride in being a Marine, and the fact that he knew he didn't want to let any of his fellow Marines down, helped him get through some of the harder times."
Hekmati's family members have told news outlets that he was kept in solitary confinement and tortured with tasers, beaten with cables, and drugged. He was also psychologically tortured.
Neller said Hekmati's captors took notice that he was a Marine.
Hekmati being a Marine was not lost on his captors.
"They would say, 'Oh, you know, you're a Marine...when they wanted to, kind of, put the pressure on him," he said.
"He's a very strong man, and we're just glad he's home and we're proud of him," Neller added.
"We're going to keep him involved in the business, whatever he does, I think he's going to go to school and continue to live the rest of life, but as he would say, he's still a Marine."