"I will say that Lance is happier than he has ever been," Lehmkuhl, winner of season four of CBS' "Amazing Race," tells "Access Hollywood" in an interview that was to air Friday.
"It has been a long ride and it's a huge relief, and I couldn't be happier for him and I couldn't be more proud of him," Lehmkuhl, 32, says.
Earlier this week, Bass, 27, told People magazine he had decided to "speak my mind" because rumors about his sexuality were starting to affect his daily life. The singer also said he is in a "very stable" relationship with Lehmkuhl.
Bass, who formed 'N Sync with Justin Timberlake, JC Chasez, Joey Fatone and Chris Kirkpatrick, said he didn't earlier disclose that he is gay for fear of affecting the group's popularity.
'N Sync, known for a string of hits including "Bye Bye Bye" and "It's Gonna Be Me," went on hiatus in 2002. Bass made headlines that year for undertaking astronaut training and failing to raise money for a trip into space.
Fatone and Timberlake have said they support their former bandmate.
"Lance is one of my great friends," Timberlake said in a statement issued by his representative, Ken Sunshine. "I support him and wish him all the happiness in the world."
Lehmkuhl tells "Access Hollywood" that Bass' sexuality will not affect his career. "No, not at all," he says. "I think it is always best in your career to be honest.
"He is going to have more support and more happiness and more freedom than he has ever had before and it is going to be a liberating experience. I guarantee it."
"The thing is, I'm not ashamed — that's the one thing I went to say," Bass says. "I don't think it's wrong, I'm not devastated going through this. I'm more liberated and happy than I've been my whole life. I'm just happy."