After studying Dutch and International Law at the University of Amsterdam, Maarten Pijnenburg was sworn in as a lawyer in Utrecht in 1990. Since he moved to Amsterdam, he has focused almost exclusively on handling criminal cases, with an emphasis on comprehensive and complicated criminal cases. In addition, he is particularly interested in defending journalists who are prosecuted in the exercise of their profession, or who are otherwise obstructed in their work (see publications). Maarten does not like to speak in public about the cases he handles, unless the interests of the client(s) must require it. In 2000, he was involved in the establishment of Keizer Lawyers.

In 2010, this firm was continued under the name Pijnenburg by a group of passionate lawyers. In addition to his work as a lawyer, he is actively involved in the training institute CaPijn, which he co-founded and which focuses on organising legal courses in the Netherlands and abroad.

Maarten Pijnenburg is a member of the Dutch Association of Defence Lawyers (NVSA) and participates in various international lawyer networks