India's Hindus have dropped below 80 percent of the population for the first time since independence and media had speculated the previous government deliberately delayed the release of the data because it showed a rise in the Muslim population.
Members of Prime Minister Narendra Modi's ruling Hindu nationalist party, which swept to power last year, have expressed growing concern about the rising numbers of Muslims.
The census data shows that Hindus declined to 79.8 percent of the country's 1.2 billion people in 2011, from 80.5 percent a decade earlier.
The share of Muslims rose to 14.2 percent from 13.4 percent in 2001 - the only major religious group to record a rise. Christians stayed at 2.3 percent and Sikhs fell to 1.7 percent from 1.9 percent.
Sakshi Maharaj, a Hindu priest-turned-politician, caused an uproar earlier this year when he said Hindu women should give birth to four children to ensure that their religion survives.