Using hourly and weekly wages from the Canadian Labour Force Survey from 2000 until 2018, workers were separated into full-time and part-time and the following striking observation was documented. The overall gender wage gap is larger than either the full-time pay gap or the part-time pay gap, even after controlling for detailed personal and job characteristics. This result is a consequence of two findings: (i) part-time wages are lower than full-time wages, and (ii) the majority of part-time workers are women. In aggregation, this brings down the average female wage, leading to a larger aggregate gender wage gap. This was further linked to a differential selection by gender into full-time and part-time work, with women of higher earnings potential being overrepresented in the pool of part-time workers, resulting in no gender pay gap in the part-time worker category. Policies targeted at encouraging full-time employment for women should therefore reduce the gender wage gap.