President Pranab Mukherjee swore in the new junior ministers at a ceremony at the president's palace Tuesday.
The expansion is seen as Modi's attempt to woo lower caste voters to support his ruling Bharatiya Janata Party in important state legislative elections early next year in Uttar Pradesh, Gujarat and Punjab states, the Associated Press reported.
Modi described Tuesday's changes as an expansion and not a reshuffle of his Cabinet. He said his government intended to ensure speed and focus in development work.
The portfolios of the new ministers are expected to be announced later Tuesday.