Born at Penshurst, Kent, he was the eldest son of Sir Henry Sidney and Lady Mary Dudley. His mother was the daughter of John Dudley, Duke of Northumberland, and the sister of Robert Dudley, Earl of Leicester. His younger sister, Mary Sidney, married Henry Herbert, 2nd Earl of Pembroke. She was important as a translator and as a patron of poetry; Sidney dedicated his longest work, the Arcadia, to her.

Philip was educated at Shrewsbury School and Christ Church College, Oxford. He was much travelled and highly learned. He was knighted in 1582, and three years later became governor of Flushing in the Netherlands. He married Frances, daughter of Sir Francis Walsingham.

Sir Philip's life ended prematurely when he suffered a fatal wound at the Battle of Zutphen. His great work, Arcadia, was only published after his death