"My prayers and solidarity with those who lost their loved ones in the unfortunate bus accident in Uttarkashi. May the injured recover soon," Modi said in a tweet.
He also announced Rs 50,000 from the Prime Minister's National Relief Fund for those seriously injured.
At least 24 persons were killed and eight others injured when the bus carrying pilgrims from Indore, Madhya Pradesh, plunged into a deep gorge late on Tuesday.
The accident took place near Nalupani when they were returning from the Gangotri shrine.