The figures include past due payments on loans worth at least 20,000 lei (EUR4.702).
Payments overdue by more than 30 days stood at RON6.45 billion in May, up from RON6.23 billion a month earlier.
Out of the total payments overdue by more than 30 days, some RON3 billion were past due payments in Romanian lei, central bank data showed.
Total overdue loan payments reached 1.049 million end-May, up from 1.042 million in the previous month.