A source close to Wasserstein said the 55-year-old single mother was diagnosed with leukemia and has not been able to receive chemotherapy because of an infection, the New York Daily News reported.
"There's a percentage chance of survival," the source said, "and our hope is that she can fight this off. But it's very serious."
Wasserstein won a 1989 Pulitzer Prize and Tony Award for "The Heidi Chronicles."
Her eighth play to be staged in New York is "Third," starring Dianne Wiest.