RBS will retain control of Ulster Bank and said it has a good market position that can deliver attractive returns.
RBS had been carrying out a review that could have seen the Ulster Bank business in the Republic of Ireland sold off.
Ross McEwan, RBS chief executive, said: “We have confirmed today that Ulster Bank remains a core part of our bank.”
Ulster Bank is the largest bank in Northern Ireland and the third biggest in the Republic of Ireland.
Ulster Bank reported an operating profit of £394m in the third quarter of 2014.
That is compared to a £58m profit in the previous quarter.
That performance was heavily influenced by an improving property market, particularly in Dublin.
It allowed the bank to “write back” £318m of impairment charges.
That means money that had been set aside to cover expected bad loans can now be released.
The bank had an underlying quarterly profit of £64m before the write backs are included.
Ulster Bank chief executive Jim Brown said this was the third profitable quarter in a row and “a clear signal that our strategy is working”.
“We will continue with our dual strategy of building a challenger bank in the Republic of Ireland and strengthen our market leading position in Northern Ireland as we progress closer alignment with RBS in Great Britain.”
He told BBC’s Good Morning Ulster that the news confirmed that Ulster Bank is “core to RBS”.
“I think there are several reasons for that,” he added. “We have a very good market position right across the island of Ireland, we’re a good strategic fit with the rest of the RBS group and the business sees great opportunities in the market as well.”
The bank’s biggest problems in recent years have been in the Dublin-based part of the business.
At one stage, it appeared as though RBS was planning to sell that part of the business or merge it with another lender.