Background: It is well established that fatherhood has a long term positive and protective effect on men's health. However, there is also evidence that the transition to fatherhood can be complex and demanding and can lead to distress, anxiety and increased risk of depression. Objective: This study aimed to investigate the prevalence of paternal postnatal depression, and to examine associations with a range of demographic and clinical factors. Methods: A cross-sectional study design was used to collect primary data from 100 fathers, whose partner gave birth to an infant in the previous 12 months. Data were collected using the Edinburgh Postnatal Depression Scale. Results: The prevalence of paternal postnatal depression was 12% using the Edinburgh Postnatal Depression Scale cut off score of 12 or above, when the cut off score was reduced to 9 or above the prevalence was 28%. The factors found to increase the risk of paternal postnatal depression included having an infant with sleep problems, a previous history of depression, a lack of social support, poor economic circumstances, not having paternity leave and not being married. Conclusion: The results add to the growing body of evidence that paternal postnatal mental health is a significant public health issue, and indicates a need for assessment and support for fathers during this life stage.