"Kavita Karkare has been declared brain dead on Monday morning," a statement from P D Hinduja Hospital and Medical Research Center, where she was undergoing treatment, said.
Kavita (57) was admitted to the hospital on Saturday after she suffered brain hemorrhage. Later she slipped into coma.
Her children -- two daughters and a son -- had consented to donate her organs to needy persons, the statement from the hospital said.
She had also been demanding better weapons, training and facilities for police personnel after her husband's killing.
Her husband was killed by terrorists near Mumbai's Cama Hospital, along with Additional Police Commissioner Ashok Kamte and senior police inspector Vijay Salaskar on the fateful night.