[1] Malcolm was elected Member of Parliament for Boston in 1860, resigning in 1878 by becoming Steward of the Manor of Northstead.
He was appointed a Companion of the Order of the Bath in 1892[2] and raised to the peerage as Baron Malcolm of Poltalloch, in the County of Argyll, in 1896.
[3] He was a Captain of the Kent Artillery Militia and Honourable Colonel of the 5th Voluntary Battalion, Argyll and Sutherland Highlanders.
After her death in October 1896 he married secondly Marie Jane Lilian, widow of H. Gardner Lister, in 1897.
[4] He left his estate to his younger brother Colonel Edward Donald Malcolm (1837–1930), who also succeeded as Laird of Poltalloch.