UCO Bank reported a fourth-quarter net loss of Rs 17.15 billion ($257 million) as its provisions for bad loans surged.
Shares of the state-run lender fell more than 6 percent after the results.
The Kolkata-based bank had reported a net profit of Rs 2.09 billion in the year-ago quarter.
Its gross bad loans as a percentage of total loans increased to 15.43 percent in March from 10.98 percent as of December.
Five other state-run banks, including second-biggest Bank of Baroda, are due to report fourth-quarter results on Friday.