Graves, eldest son of the writer Alfred Perceval Graves (1846 - 1931), was born in Ballylickey Manor, County Cork, Ireland, into a prominent Anglo-Irish family. He studied in Haileybury and Oxford University. He was the elder half brother of author Robert Graves.

As a correspondent of The Times in Constantinople from 1908 to 1914, he reported on the events preceding World War I. In 1914, as a British citizen, he had to leave the Ottoman Empire due to the war. In 1915-1919, he served in the British Army in the Middle East war theatre. As a captain in Army Intelligence in Cairo he worked with T. E. Lawrence on the Turkish Army Manual for the Arab Bureau. His uncle Sir Robert Windham Graves had been British Consul in Erzurum (1895) and financial adviser to the Turkish government (1912) and worked for Civil Intelligence in Cairo during the same period.After 1919, Graves reported from his own homeland on the Anglo-Irish War. He knew Michael Collins, W. T. Cosgrave and the various Irish leaders and was closely involved in reporting events in this critical period of Irish history. He later worked as a foreign correspondent in India, the Levant and in the Balkans and before returning to London to work as an editor of The Times.

In 1921 he exposed The Protocols of the Elders of Zion as antisemitic plagiarism in a series of articles in The Times.

His most monumental work was a 21-volume history of World War II. Graves received numerous international awards and titles, among which are French Légion d'honneur and Order of the Crown of Italy.

In his journeys, Philip Graves developed an interest in entomology and published articles in scientific journals. He was member of the Royal Irish Academy.

He retired in 1946 to Ballylickey Manor and dedicated himself mainly to zoological hobbies. Here he made a study of the Irish butterflies, being especially interested in the local sub-species. He restored Ballylickey House as a hotel, which was taken over by his son after his death.

Graves specialised in butterflies (Lepidoptera) of Syria, Lebanon, Iraq, and Palestine, often working with Robert Eldon Ellison, a career diplomat andfellow Irishman (born in Wingstown, near Dublin).

His published work on insects reflects the strengths of his collection but not its extent. In 1938, for instance, he presented more than 2,500 specimens to the Natural History Museum, London. These are described in the catalogue of acquisitions Rhopalocera (Levant and Balkans). There are a few specimens, including an excellent series of Archon apollinus in the Ulster Museum, Belfast.

His published work on insects includes:

• Collecting Lepidoptera in Syria, 1905 Entomologist’s Rec. J. Var 18:125-6 (1906).
• Collecting in Syria: Ain Zhalta in May -June 1905. Entomologist’s Rec. J. Var 18:149-152 (1906).
• A contribution to the fauna of Syria Entomologist’s Rec. J. Var 23: 31-36 (1910).
• Two new Lycaenid subspecies from the Lebanon Entomologist 56: 154-157(1925).
• The Rhopalocera and Grypocera of Palestine and Transjordania Trans. Ent. Soc., London, 1925 17-125 (1925).
• with Ellison, R.E. The butterflies of the Jabal Quinesia, Lebanon Entomologist’s Rec. J. Var 40:177-180 ( 1938).

An account of Graves work in entomology is given in Hesselbarth, G.; Oorschot, H. van & Wagener, S., 1975 Die Schmetterlinge der Türkei, Band 2: 1179 - 1199 [B 2189:2].

He is commemorated in the subspecies of the Brimstone butterfly found in Ireland, Gonepteryx rhamni gravesi Huggins, 1956.