Background. The impact of cancer on spouses of cancer patients may be considerable in many aspects. Our objective was to evaluate sick leave in spouses of cancer patients before and after the diagnosis. Material and methods. Using Swedish population-based registries, we studied sick leave of spouses to patients with newly diagnosed colon, rectal, lung, prostate, or breast cancer. We identified the cancer patients via the Swedish Cancer Registry and obtained information of their spouse through linkage with the population register. We assessed the number of sick leave episodes and sick days one year before until one year after the spouses' cancer diagnosis by cross-referencing with Swedish Social Insurance Agency data. We also compared the number of sick days of spouses with the general population adjusted for age, sex and partner status. Results. In general, spouses (N=1 923) to cancer patients had an increase in the frequency of new episodes of sick leave in the months before and after the cancer diagnosis. Spouses of lung cancer patients had most sick leave episodes, and the largest number of sick days per person. In comparison to the general population, spouses in the lung cancer group also had the highest standardised sick day ratio 1.76; 95% confidence interval 1.24, 2.40. The corresponding risk for spouses in other groups of cancer was not significantly increased. Discussion. In Sweden there is often increased sick leave of spouses to cancer patients. It may be due to emotional stress and physical reactions that follow with cancer which needs to be further explored in order to provide adequate support and care.