Despite the limited and relatively weak empirical evidence for the effectiveness of part-time sick leave, the Swedish government has promoted the use of part-time sick leave instead of full-time sick leave, when possible. Our paper brings some empirical evidence for the importance of part-time sick leave on the return to work before it was included in a governmental plan to increase health in the working life and to reduce sick leave. Using a unique data set that combines register and survey data, we examine the effects of being on part-time sick leave compared to full-time sick leave on the probability of full recovery of temporarily lost work capacity. Using a discrete choice factor model that accounts for the selection into the degree of sickness (part-time or full-time), we found that the mean treatment effect of a (by definition) random assignment is negative for relatively shorter spells and almost zero for spells longer than 90 days. In contrast, the mean treatment effect of selective assignment (i.e., only for those who were actually “treated” with part-time) is negative for spells up to 120 days but positive afterwards. This suggests that part-time sick leave could be used for cases lasting longer than 120 days as a gradual return to work after about four months of full-time sick leave. Therefore, part-time sick leave could be tested to help employees on sick leave because of post-Covid conditions (or long Covid) to gradually return to work.