Background With early diagnosis, improvements in treatment of cancer, and better survival rates, more men of reproductive age are long-term survivors. The trends in birth rates among male cancer survivors were assessed in this study. Methods From the Swedish Multi-generation Register and the Cancer Register we identified 67,740 men aged 70 years or younger with a history of cancer, for whom we calculated birth rates relative to the background population (standardised birth rates, SBRs). Independent factors associated with reduced birth rates among cancer survivors were estimated by use of Poisson modelling. Findings Overall 7.3% of men with a history of cancer had partners who gave birth after their diagnosis. These men were 23% less likely to father a child than were those in the background population. Men with breast, skin, and thoracic cancers had SBRs similar to the background population, whereas those with prostate, brain and eye, reproductive, and haemopoietic cancers were the most affected, having low SBRs. Nulliparous men were significantly more likely to father a child (SBR 0.80, 95% confidence interval (CI) 0.78–0.82) than were those who were parous (SBR 0.69, 95% CI 0.66–0.72), and at seven of 12 sites nulliparous men had birth rates similar to men in the background population. Cancer site (prostate), age at onset of cancer (<12 years), parity status (parous), current age (>40 years), and a recent diagnosis were significant and independent predictors of a reduced probability of fathering a child after diagnosis. Interpretation Male cancer survivors are less likely to father a child than are men in the background population. Fertility is affected by the cancer site, age of onset, and parity status at diagnosis. The authors declared no conflicts of interest. With early diagnosis, improvements in treatment of cancer, and better survival rates, more men of reproductive age are long-term survivors. The trends in birth rates among male cancer survivors were assessed in this study. From the Swedish Multi-generation Register and the Cancer Register we identified 67,740 men aged 70 years or younger with a history of cancer, for whom we calculated birth rates relative to the background population (standardised birth rates, SBRs). Independent factors associated with reduced birth rates among cancer survivors were estimated by use of Poisson modelling. Overall 7.3% of men with a history of cancer had partners who gave birth after their diagnosis. These men were 23% less likely to father a child than were those in the background population. Men with breast, skin, and thoracic cancers had SBRs similar to the background population, whereas those with prostate, brain and eye, reproductive, and haemopoietic cancers were the most affected, having low SBRs. Nulliparous men were significantly more likely to father a child (SBR 0.80, 95% confidence interval (CI) 0.78–0.82) than were those who were parous (SBR 0.69, 95% CI 0.66–0.72), and at seven of 12 sites nulliparous men had birth rates similar to men in the background population. Cancer site (prostate), age at onset of cancer (<12 years), parity status (parous), current age (>40 years), and a recent diagnosis were significant and independent predictors of a reduced probability of fathering a child after diagnosis. Male cancer survivors are less likely to father a child than are men in the background population. Fertility is affected by the cancer site, age of onset, and parity status at diagnosis. The authors declared no conflicts of interest.