He works as the coach of the Under-18 squad of FC Eindhoven He represented the Netherlands national team at the 1978 FIFA World Cup in Argentina.

After his retirement in the early 1990s, he became a football manager and worked for clubs such as Den Bosch, RBC Roosendaal, Telstar and Southampton.

On 29 May 2008, he was announced as the new head coach of English Football League Championship side Southampton as an immediate replacement to Nigel Pearson, with Mark Wotte taking over the Academy.

However, three days later, Poortvliet recorded his first win as Southampton manager, beating Exeter City 3–1 in the League Cup first round.

In June 2010, he was introduced as new head coach of Telstar, another Dutch Eerste Divisie team; his salary will however be paid by parent club AZ.