In many Western countries, including the Netherlands, couples marrying in the interwar period experienced unprecedentedly high levels of childlessness. Only recently do we witness a return to these levels, as part and parcel of the so-called second demographic transition. Looking back on the interwar period, many scholars have attributed the decline of fertility and the increase of childlessness to rampant economic and political instability. However, contemporary social scientists ascribed the phenomenon to individualization, secularization, and the priority newlywed couples gave to a career and a luxurious lifestyle. From this perspective, childless couples in the interwar period could be seen as “pioneers” of the second demographic transition. To disentangle “traditional” and “modern” backgrounds of childlessness, we have studied the fertility histories of nearly 3,000 Dutch couples married between 1919 and 1938. Our results, in particular the strong association of childlessness with religiously mixed marriage, confirm that an important part of childlessness in the interwar period can be associated with a modern, individualized lifestyle.