Antonio van Diemen was born in 1593 at Culemborg, Holland, the son of Bartholomeus van Diemen and Elisabeth Hoevenaar. His parents were able to provide him with a good education and hoped that one day their son would become Mayor of Culemborg. Antonio though had other plans. In 1616 he became a merchant and moved to Amsterdam. It turned out a disaster and he went broke a year later. To be able to pay his creditors he decided to move to Batavia, the capital of the Dutch colony of Indonesia in an effort to find work at the Dutch East Indie Company (VOC). This company was not inclined to employ any bankrupts and van Diemen took on the pseudonym of Thonis Meeusz.
On 4 January he gained a job on the ship Mauritius and arrived in Indonesia on 22 August 1619. Although Governor Jan Pieterszoon Coen had been informed and knew who Meeusz was he still employed him in the public service. Before leaving the colony, Coen promoted van Diemen under his own name and by 1626 van Diemen was again promoted, this time he became Director General of Commerce and member of the Council for Indie.
On 17 January 1630, van Diemen married Maria van Aelst, widow of Bartholomeus Kunst. A year later van Diemen returned to Holland as Admiral on the ship Deventer. In 1632 he returned to Batavia and was appointed Governor General of Indie on 1 January 1636. His nine years as governor were successful and important for both the colony and the commercial success of the East Indie Company. It was van Diemen who devoted most of his energy to expanding the power of the Dutch and particularly that of the VOC. Under his rule Dutch power was established in Ceylon for the next 150 years.
His first successful action resulted in the freedom of Pieter Nuyts, who had been imprisoned for the last five years. His best known instruction was to order Frans Jacobszoon Visscher to draw up a plan for discoveries in the south. Visscher mapped out three different routes and van Diemen decided on 1 August 1642 to send Abel Tasman in search of the Great South Land.
When van Diemen died on 19 April 1645, his wife returned to Holland, with numerous presents and a large financial gift from the East Indie Company. She married, for a third time on 6 September 1646, Carel Constant from Middelburg.