Dutch law makes no stipulation regarding the nationality of crew members, with the exception of the master, who is required to be Dutch. Persons who are nationals of any of the Member State countries of the European Union or of one of the other states which are party to the Agreement on the European Economic Area, are exempted from the nationality requirement. However, if shipowners can demonstrate that despite their best efforts to do so, it is not possible to employ a master from one of these nationalities, they may ask for approval to employ non-European masters.
To employ foreign seafarers on board Dutch flagged vessels a shipowner needs to apply for a licence based on the collective labour agreement between the Royal Dutch Shipowners Association (KVNR, representing the employers) and Nautilus International (representing the employees).
For this procedure, please see: https://www.kvnr.nl/en/licences