Pedro de Alberni was born in 1747 in the city of Tortosa in the Catalonian province of Tarragona. The young Catalán began his military career in July of 1762 as a cadet in the 2nd Regiment of Light Infantry of Catalonia and participated in the invasion of Portugal during the Seven Year's War. After nearly 5 years service with his unit, he received promotion to subteniente and was transferred 4th in command of the primera compañia franca de Voluntarios de Cataluña. This Catalonian military unit received orders to prepare for service in the Americas and sailed from Cadiz to Mexico in May of 1767. Alberni soon saw action in northwestern Mexico with the Catalonian Volunteers during the Sonoran Desert Expedition of 1767-1771. With the completion of the campaign he was assigned for a short period to the capital of Mexico as 2nd in command of the Catalonian Volunteers. In 1776, he was promoted to teniente and 2 years later to capitán graduado. In 1782 Alberni assumed command of the Catolonian Volunteers of the military garrison of Nayarit on the Pacific Coast. Here he married Juana Velez from the provincial capital of Tepic.
In 1790 Alberni's command was assigned to the Pacific Northwest and the establishment of fortifications at Nootka on the west coast of Vancouver Island. These troops also participated in expeditions to Alaska and the west coast of Canada, specifically in the Strait of Juan de Fuca, to reinforce Spain's claim to the Pacific Northwest.
As a result of his distinguished service for two years and ten months in this remote and harsh place in the world, Alberni and what was left of the primera compañia franca de Voluntarios de Cataluña were withdrawn from Nootka near the end of 1792.
On arriving back in Mexico he had little time to rest and was assigned as comandante de armas of the Castillo de San Juan de Ulúa and teniente del Rey of the plaza de Veracruz, where he served for eight months. He served for two years in Guadalajara where devoted some time to his family.
Near the end of 1795 Alberni and 72 Catalonian Volunteers were assigned to Alta California, where he received appointment as comandante de armas of the four presidios of Alta California. A year later Alberni was commandant of the San Francisco Presidio and as lieutenant colonel in the Army, made him the highest-ranking military figure in California at that time.
On the ill health of the California governor
Diego de Borica, Alberni was assigned to Monterey Presidio in
January 1800. However, soon after arrival he was taken ill by
a severe condition of dropsy (hidropesía). Knowing that
the end was rapidly approaching, he made out a will on December
15, 1801 at the nearby San Carlos Mission at Carmel, leaving his
entire estate to his wife, as their daughter had died earlier.
Alberni appointed Sergeant Tico as administrator of the will.
He received the rites of extreme unction on March 11, 1802 and
died at age fifty-five, and was buried at the Mission.