The upgrade in outlook follows the government's announcement last month to infuse an unprecedented Rs 2.1 lakh crore into public sector banks over two years.
"Moody's changed the outlook to stable from negative for BoI (Bank of India) and its London and Jersey branch, Union Bank and its Hong Kong branch, and OBC (Oriental Bank of Commerce)," Moody's said in a statement.
The US-based ratings agency also affirmed local and foreign currency bank deposit ratings of these three PSU banks.
Moody's has also affirmed the standalone credit profiles or baseline credit assessments (BCAs) of these three banks.