Joost has been active in venture capital and private equity all his professional life.

A Dutch citizen, he joined Oranje – Nassau Groep BV in 1976 and was responsible for setting up its venture capital and private equity business in Holland (Investeringen Oranje Nassau), France (Alpha Associes) , Belgium (Advent Belgium), the Far East (SEAVI in Singapore and ChinaVest in Hong Kong and Shanghai) and the US (Investments Orange Nassau Inc and Advent International in Boston).

He lived in Boston from 1980 until he moved back to Holland in 1993 to run Janivo Holding BV, a privately held investment company. Companies that he helped set up as an early investor include Biogen Idec (1978, biotechnology), Edap SA (1984, medical technology) and Tele Atlas BV (1989, digitised mapping).

Joost left Janivo in 2010 and is currently involved as an investor in several, mostly Dutch companies. He has been a board member of Naseba since 2011.

Joost resides in Bloemendaal (near Amsterdam) with his wife.