Joan (or Johan) van Hoorn was born on 16 November 1653, son to the wealthy Amsterdam gunpowder manufacturer, Pieter Janszn van Hoorn and his wife Sara Bessels, a grandchild of Gerard Reynst.

As the gunpowder trade was no longer doing so well, his influential friends got him named as Counsellor-extraordinary (Raad extraordinair) to the Dutch Council of the Indies.

In 1665, when he was still only 12 years old, Joan van Hoorn was already Under-assistant (onder-assistant) in the Dutch East India Company (VOC).

From July 1666 until January 1668, he accompanied his father on a mission to China, where he was received by the Kangxi Emperor.

A further visit to Bantam took place in 1685, following which he was named full Counsellor (Raad ordinair) of the Indies.

Following the death of his wife, he remarried, in 1692, this time to Susanna, the daughter of the then Governor-General Willem van Outhoorn.

The Seventeen Lords (Heren XVII) acceded to this demand and on 15 August 1704, Joan van Hoorn accepted the post of Governor General.

In 1705, Joan van Hoorn concluded an agreement with Mataram, which ceded West Java to the Company.