The German manufacturer said 11 million of its vehicles were affected worldwide - including almost 1.2 million in the UK.
A Government report published in April 2016 showed diesel cars being sold in the UK emit an average of six times more NOx in real-world driving than the legal limit used in official tests.
Dr Dieter Zetsche, chairman of the board of management of Daimler AG and head of Mercedes-Benz Cars, said: "The public debate about diesel engines is creating uncertainty - especially for our customers.
"We have therefore decided on additional measures to reassure drivers of diesel cars and to strengthen confidence in diesel technology.
"We are convinced that diesel engines will continue to be a fixed element of the drive-system mix, not least due to their low CO2 emissions."
Over 170,000 Mercedes cars were registered in the UK last year alone.
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