Average card debt per borrower was up slightly in the second quarter, rising about 0.2 percent to $5,234. It rose 1.4 percent from the first quarter of this year.
Americans still have a limited appetite for debt after gorging themselves on sub-prime mortgages and credit cards before recession seized the country in late 2007.
Credit card borrowing started rising again in 2011, but the increases have lagged far behind other types of debt, including auto and student loans.
All told, U.S. credit card debt has increased 1.3 percent over the past year, reaching $873.1 billion in June, according to the Federal Reserve.
Meanwhile, the number of new credit card accounts opened by consumers increased in the first three months of the year.
The data lag by a quarter, so the latest TransUnion figures cover the January-March period. They show that the number of new credit card accounts rose 17.8 percent to about 11.7 million versus the same period a year earlier.
The share of cards issued to borrowers with less-than-perfect credit increased to 31.2 percent, compared with 27.3 percent a year earlier.
That's still well below the roughly 45 percent share of cards going to non-prime borrowers before the recession, however.
In the VantageScore credit rating scale, consumers with a score lower than 700 on a scale of 501-990 are considered non-prime borrowers.
Lenders also are being more generous with the amount of credit they extend to cardholders.
The average credit limit on new bankcard accounts has increased steadily, rising 29.4 percent to $5,230 over the three-year period ended March 31, TransUnion said.
The increase in card credit limits points to lenders feeling they can take on more risk while giving consumers a bigger credit cushion, said Tony Guitart, TransUnion's director of research and consulting.