Haney also told The Golf Channel that he saw no hint of world No. 1 Woods taking any sort of performance-enhancing drugs, including during sessions with controversial Canadian doctor Anthony Galea.
The revelations were shown in video clips posted on The Golf Channel website promoting a full interview with Haney to be aired Sunday night on the network.
Woods, whose admission of multiple mistresses shattered his world on and off the course, had never said he was receiving his therapy for sex addiction, although he had been photographed at a Mississippi clinic known for such treatment.
Asked why Woods spent six weeks in a treatment facility, Haney replied, "The only thing that I knew about was his issue with the sex addiction."
"It's an ongoing day-to-day battle, but so far I think he's doing a really good job. He's making progress," Haney said. "Hopefully he'll be able to do what he needs to do."
Haney announced Monday that he was resigning as Woods' swing coach and Woods said Tuesday the two had parted ways on good terms.
More than a dozen women have claimed to have had sexual affairs with Woods, a married father of two who returned to golf last month and tied for fourth at the Masters.
But Woods missed the cut two weeks ago at Charlotte and withdrew from last week's Players Championship after seven holes of the final round with an inflamed neck joint.
Reports have Woods and wife Elin set to divorce with the U.S. tabloid National Enquirer , which broke the story of Woods' first infidelity last November, saying Woods admitted in therapy to having been with as many as 120 women during their five years of marriage.
"The one (issue) he's dealing with is not easy to overcome," Haney said.
Federal investigators are looking into the activities of Galea for providing banned performance-enhancing substances to athletes.
Woods said he has never taken any banned substances and his dealings with Galea never involved doping or drugs, only a process known as blood spinning that Woods hoped might help him heal faster from a 2008 knee injury.
Haney backed up Woods, denials, saying that he saw no wrongdoing and he was at four of the five sessions Galea spent with Woods.
"There was never anything that went into Tiger Woods' body that didn't come out of his body," Haney said. "I spent 110 days with Tiger a year for six years. I spent probably 40 to 50 nights a year at his house. I've never seen him do any (performance-enhancing drugs). He has never talked about anything."
Exactly when Woods might return to competitive golf from his neck injury remains uncertain. He is entered in next month's U.S. Open at Pebble Beach, where he won by 15 strokes in 2000, and the PGA National in July.
"There's a lot of things going on in my life, period, right now," Woods said in a website posting. "I'm trying everything I can to get back as soon as I can, just trying to get everything in a harmonious spot and that's not easy."