Pieter Marinus Seelaar started playing cricket at the Under-15 level, followed by Under-17 and Under-19 level before making his senior debut in a C&G Trophy game against Warwickshire on 3 May 2005. He then made hisODI debut against Sri Lanka on 6 July 2006 followed by a T20I debut two years later.
In Netherlands' historic opening game of the 2009 World T20 which saw them achieving a spectacular win over England, Seelaar dismissed skipper Paul Collingwood and earned much praise. Earlier he had missed out on the 2007 ODI World Cup but was a part of the squad during the 2011 tournament. He is best known during that time for dismissing Kevin Pietersen and Sachin Tendulkar and finishing as his team's leading wicket taker with 8 scalps.