The present study was designed to investigate the relationships among mindfulness, happiness, and the expression of pet peeves. Previous research has established a positive correlation between happiness and mindfulness, but, to date, no research has examined how each of these variables is related to complaining in the form of pet peeves. Four hundred ten male and female college students listed the pet peeves they had with a current or former relationship partner. They also completed measures of happiness, positive and negative affect, depression, mindfulness, relationship satisfaction, and satisfaction with life. Pet peeves were negatively correlated with relationship satisfaction, well-being, and mindfulness. Consistent with hypotheses, support was found for the mediating role of mindfulness in the relationship between happiness and pet peeves.