Dundas was appointed Second Naval Lord in the First Palmerston ministry in April 1857 and then First Naval Lord in the same ministry in November 1857. Promoted to vice-admiral on 24 February 1858, Dundas stepped down to be Second Naval Lord in the Second Derby ministry in March 1858. He stepped up again to become First Naval Lord in the Second Palmerston ministry in June 1859 remaining in office until his death. He died, unmarried, of a heart attack at Spring Gardens in London on 3 June 1861. Later that day, the Prime-Minister (Viscount Palmerston) described Vice Admiral Dundas as: