It "wasn't an overdose," he told the newspaper. "My daughter is very down right now. None of us are OK."
Harrison Police Chief David Hall refuted Thomas' claim about his daughter to the New York Times on Friday night.
"I understand that this person claims it was his daughter; he is lying," Hall told the newspaper. "It was definitely not his daughter, it was a male. We know the difference between a 47-year-old black male and a young black female."
Hall had earlier said the case was not a suicide attempt.
"We're classifying it as an accidental overdose of prescription sleeping pills," Hall said. "I'm not going to confirm or deny that it was Isiah Thomas. It was an individual at his home."
He told The Daily News that the man took about 10 Lunesta sleeping pills. "He was unconscious, but breathing on his own," Hall told the paper.
Thomas' 20-year-old son Joshua also said it was his sister, not his father, who required treatment.
"He's fine," the Indiana University student told the Daily News. "Reports of sleeping pills are false."
The drama is the latest in what has been a difficult year for Thomas.
He was fired as the Knicks coach on April 18 after a season of dreadful basketball, a tawdry sexual harassment lawsuit and unending chants from fans demanding his dismissal. Still, he was retained by the organization as an adviser and consultant to Donnie Walsh - who had replaced him as president as basketball operations.
Walsh said he had not spoken to Thomas, though others in the organization had.
"Isiah Thomas spoke with members of the New York Knicks organization and is OK," the Knicks said in a statement. "He is dealing with a family matter, and we will have no further comment. He has asked that we respect his privacy, and we will."
Messages left with Thomas' publicist and two of his attorneys weren't returned.
Hall said an ambulance and two police officers responded to a 911 call that came in from the Thomas home a couple minutes after midnight. The victim was taken to White Plains Hospital Center, about 5 miles from the home.
Officials there would not say whether Thomas was a patient, or identify the overdose patient. And officials with Harrison's Emergency Medical Service declined to say what happened, citing medical privacy laws.
"There's a concern, I'm sure everybody I would think is wishing for the best for his family but again ... I don't really know a whole lot," Knicks coach Mike D'Antoni said.
Late Friday afternoon, a small SUV escorted by a police car pulled into a private road leading to the luxury cul de sac of multimillion-dollar homes in Westchester County where Thomas lives, about 30 miles from midtown Manhattan.
Thomas purchased the house on Azalea Circle in Purchase for more than $4 million in 2004, according to the Journal News.
Thomas brought most of the current Knicks to New York, and some said they have spoken to him since last season ended. Forward Quentin Richardson said he has called Thomas from time to time.
"This is our former coach, still a good friend and somebody I still look up to to this day. I mean, a Hall of Famer and all those different things," Richardson said at Madison Square Garden before the Knicks' exhibition game against New Jersey.
"This is life, this is something that happened. It's an unfortunate situation, and we still don't know the exact story or whatever happened. But I don't look at something like this as a distraction; this is an unfortunate incident."
As a player, Thomas was one of the NBA's great point guards, winning NBA titles with the Detroit in 1989 and 1990. In college, he led Indiana to a national championship in 1981.
He joined the Knicks as the team president in December 2003 and became coach in June 2006 after Larry Brown was fired.
Last season, the Knicks' woes earned Thomas the wrath of fans, who serenaded him nightly with chants of "Fire Isiah!" When he was dismissed, his record in New York was 56-108.
Overall, he is 187-223 as an NBA coach, leading the Indiana Pacers to the playoffs in three straight years from 2000-03.