The part-nationalised lender - which has more than 40 million customers and uses the services of over 30 brands around the world - reported reductions of Â£794 million over the six-month period, whereas profit across the same spell in 2010 came in at Â£1.2 billion.
Money spent to cover compensation paid to customers mis-sold payment protection insurance and the Greek debt write-off both played a part in the bank's half-year performance.
Despite this, RBS chief executive Stephen Hester told BBC Radio 4's Today programme that the institute's restructuring is "going well".
Mr Hester explained: "We are getting risk down, the bad assets - that have been dogging us from past years - are coming down."
Problems affecting everybody in the world banking sector are impacting banks in different ways, he added.
By Asim Shah