Research examining the impact of pet ownership on mental wellbeing is a small but expanding area of psychological research. Past studies have identified a positive relationship between pet ownership and mental wellbeing. However, research thus far has focused predominantly on the benefits of general pet ownership on mental wellbeing. Secondly, the populations investigated are predominantly confined to the U.S. The present study aims to restrict the demographic to the Irish population, and to venture from general pet ownership to the comparative effects of cat and dog ownership. This research investigated whether such a difference can be accounted for by the Big Five personality factors. Data was collected from 159 participants; 112 female, 57 male. The average age of the participants was 24. Demographic area, pet ownership information, the Emotional Quotient Inventory and the Big Five Inventory were collected via questionnaire. The results of this study do not support either of the hypotheses advanced. Statistical analyses failed to locate a significant effect of type of pet ownership on well-being or personality traits. The hypothesis that differences between cat and dog owners stemming from the five-factor model of personality remains empirically unsupported. Limitations of the present study and recommendations for future research on the relationship between pet ownership and mental wellbeing are discussed.