Vandross, who turns 52 on Sunday, suffered the stroke Wednesday at his Manhattan home, said Lois Najarian, a spokeswoman at his record label, J Records.
Najarian declined to discuss whether the R&B singer's motor skills had been impaired or the extent of the stroke. She also declined to name the hospital where Vandross was being treated.
An earlier statement from his management said family and friends were hopeful for a speedy recovery. A source close to the singer described the stroke as serious, but said Vandross was conscious.
Vandross, whose deep silky voice has anchored romantic hits such as "Here and Now," "A House Is Not a Home" and "Any Love," has sold about 20 million albums in the United States.
Najarian said the singer had been in good health and recently completed work on a new album.
But Vandross, who has suffered from hypertension and diabetes, has long battled weight problems. At one point, he weighed more than 330 pounds.
"Rumors about my health always surface," he said in 2001, "because people see the weight fluctuations."
Vandross said in the interview that since he had lost weight through diet and exercise, he no longer suffered from diabetes or high blood pressure. However, he recently had gained weight again.
Vandross won four Grammy Awards in the 1990s. His new album, "Dance With My Father," was scheduled for a June 10 release.
By Nekesa Mumbi Moody