Working out of LA, the will work closely with NPA general manager John Ford, to whom she will report.
Van Kempen was co-principal and executive producer at Film Garden Entertainment, which was behind shows such as Amazing Wedding Cakes and Hogs Gone Wild.
At the NPA, which was founded in July 2014 to represent unscripted indies in the US, Van Kempen will work on all policy issues, strategy and operations, industry events and membership services.
The NPA says its member companies produce more than half of the unscripted content on US cable and broadcast television and OTT and online networks.
Its newest member, Endemol Shine North America-owned Authentic Entertainment, brought the total membership number to 37 at 2015 year-end.