Camilo de Almeida Pessanha was born the illegitimate son of Francisco António de Almeida Pessanha, an aristocratic law student, and Maria do Espírito Santo Duarte Nunes Pereira, his housekeeper, on 7 September 1867, at 11.00 p.m., in Sé Nova, Coimbra, Portugal.

In October 1889, he resumed his studies and began a close and lifelong friendship with António Osório de Castro, a fellow student and director of a paper where he published some his poems.

Pessanha also became intimate with his friend's sister, Ana de Castro Osório, a would-be writer and pioneer feminist in Portugal.

In August 1893, lured by the mysteries of the Orient,[2] Pessanha applied for a position as philosophy teacher in the newly established gymnasium of Macau, then a Portuguese colony in distant China.

During one of his stays he would have met Fernando Pessoa, an ardent admirer of Pessanha's poetry, influencing his work between 1909 and 1911; this was his Paulismo phase.

He was a respected teacher (of philosophy, history, geography, Portuguese literature, law), attorney and judge, and he was an adviser to the several governors of the city.

To pass his time, besides composing poetry, he immersed himself in the local culture, collected Chinese art and became a respected China authority in the colony.