In October 1757 Boscawen was second in command under Admiral Edward Hawke. On 7 February 1758 Boscawen was promoted to Admiral of the blue squadron. and ordered to take a fleet to North America. Once there, he took naval command at the siege of Louisburg during June and July 1758. On this occasion rather than entrust the land assault to a naval commander, the army was placed under the command of General Jeffrey Amherst and Brigadier James Wolfe. The siege of Louisburg was one of the key contributors to the capture of French possessions in Canada. Wolfe later would use Louisburg as a staging point for the siege of Quebec. The capture of the town took away from the French the only effective naval base that they had in Canada, as well as leading to the destruction of four of their ships of the line and the capture of another. On his return from North America Boscawen was awarded the Thanks of both Houses of Parliament for his service. The King made Boscawen a Privy Counsellor in recognition for his continued service both as a member of the Board of Admiralty and commander-in-chief.