He was appointed a Lord of Appeal in Ordinary in 1930, and sat as such until 1947 except for a brief period at the outbreak of World War II when he was Minister of Information.
He was appointed a Lord of Appeal in Ordinary and additionally created a life peer as Baron Macmillan, of Aberfeldy in the County of Perthshire in 1930. He sat as Lord until 1947 except for a brief period at the outbreak of World War II when he was Minister of Information.