The number of workers who hold more than one job (a.k.a. multiple jobholders) has increased spectacularly in Canada since the mid-1970s – it has been multiplied by almost three. In this paper, we document this historical change and provide a comprehensive account of its dynamics. To this end, we use restricted-access panel micro-data from the Canadian labour force survey to construct transition probabilities in and out of multiple jobholding. We analyze these data through the lens of a trend decomposition that separates out the role of worker inflows and outflows. The upward trend in multiple jobholding is chiefly explained by the increased likelihood of single jobholders to pick up second jobs. While economic reasons remain important among the motives that push workers towards multiple jobholding, a more flexible hours schedule in the main job may explain why taking on a second job has become more frequent.