On 26 May 1940, Operation Dynamo, the Evacuation of Dunkirk, began, with "Montrose" being ordered to take part. On 28 May she successfully evacuated 925 troops, landing them at Dover. She was heading out on another run to Dunkirk early in the morning of 29 May when she collided in a fog bank with the tug "Sun V", breaking the destroyer's stem. "Montrose" had to be towed back to Dover stern-first by the tug "Lady Brassey". "Montrose" was under repair at Harland and Wolff's North Woolwich yard from 31 May to 5 July 1940. After repair, "Montrose" joined the 18th Destroyer Flotilla, Nore Command, based at Harwich. In July 1940, in the first part of the Battle of Britain, German aircraft carried out a campaign of attacks against coastal shipping in the English Channel, and on 27 July, as part of this campaign, attacked "Montrose" and the destroyer , which were escorting minesweepers off Aldeburgh, Suffolk. "Montrose" claimed two German bombers shot down during the engagement, but was badly damaged by near-misses which immobilised her, while "Wren" was sunk. "Montrose" had to be towed back to Sheerness.