Although Organizational Citizenship Behaviour (OCB) has been studied extensively over the years in the US, the measurement of OCB has received relatively limited attention in other international contexts. This study investigates the dimensionality of a specific OCB measure in a Dutch-speaking context (Flemish part of Belgium). In addition, we examine the invariance of this measure across two different samples: supervisor ratings of 259 subordinates and peer ratings of 215 employees. Generally, we found clear support for the discriminant validity of five OCB factors but convergent validity was only established for three of the five factors. This measurement structure found was relatively invariant across the two different samples These results show that the forms of OCB that are predominantly studied in the US seem to hold relatively well in another international context, although there are some differences.