Campion was born in London and studied at Peterhouse, Cambridge, but left without taking a degree. He later entered Gray's Inn to study law in 1586. However, he left in 1595 without having been called to the bar. On 10 February 1605 he received his medical degree from the University of Caen.

Campion was first published as a poet in 1591 with five of his works appearing in an edition of Sir Philip Sidney's Astrophel and Stella. The Songs of Mourning: Bewailing the Untimely Death of Prince Henry (1613), were set to music by John Cooper. He also wrote a number of other poems as well as a book on poetry, Observations in the Art of English Poesie (1602), in which he criticises the practice of rhyming in poetry.

Campion wrote over one hundred lute songs in the Books of Airs, with the first collection (co-written with Philip Rosseter) appearing in 1601 and four more following throughout the 1610s. He also wrote a number of masques, including Lord Hay's Masque performed in 1607, along with Somerset Masque and The Lord's Masque which premiered in 1613. Some of Campion's works were quite ribald on the other hand, such as "Beauty, since you so much desire" (see media). In 1615 he published a book on counterpoint, A New Way of Making Fowre Parts in Counterpoint By a Most Familiar and Infallible Rule, which was regarded highly enough to be reprinted in 1660.

He was implicated in the murder of Sir Thomas Overbury, but was eventually exonerated, as it was found that he had delivered a bribe unwittingly.

Campion died in London, possibly of the plague.

Early dictionary writers, such as Fétis saw Campion as a theorist. It was much later on that people began to see him as a composer.

He was the writer of a poem, Cherry Ripe, which is not the later famous poem of that title but has several similarities.