Born in Brentford, Henderson was the eldest son of Alexander Henderson, 1st Baron Faringdon of Buscot Park in Berkshire (now Oxfordshire), and his wife Jane Ellen (née Davis). He was commissioned a second lieutenant in the 3rd (Militia) Battalion of the Royal Berkshire Regiment on 3 March 1894. He transferred to active service in the British Army when he was appointed a second lieutenant in the 1st Life Guards on 3 February 1897, and was promoted to lieutenant on 2 April 1898. With a detachment from his regiment, he served in the Second Boer War in South Africa 1899-1900, and received the Queen's South Africa Medal (with two clasps). After his return, he was on 6 September 1902 promoted to captain, and appointed adjutant of the regiment. After he resigned from the army, he received an appointment with the Territorial Army in the Berkshire Yeomanry.
He sat as Member of Parliament for Abingdon from 1910 to 1916. Henderson resigned his seat on his appointment as military secretary to the Duke of Devonshire who was to become Governor General of Canada in November 1916.
Henderson married Lady Violet Charlotte Dalzell, daughter of Robert Dalzell, 11th Earl of Carnwath, in 1901. They lived at Kitemore House at Shellingford in Berkshire (now Oxfordshire). He died in November 1922, aged 47 in Faringdon, twelve years before the death of his father. He had four children and his eldest son, Alexander Gavin, succeeded in the barony in 1934.