We examine the role of employee mindfulness in the context of highly monotonous work conditions. Integrating research on task monotony with theorizing on mindfulness, we hypothesized that mindfulness is negatively associated with the extent to which employees feel generally bored by their jobs. We further hypothesized that this lower employee boredom would relate to downstream outcomes in the form of job attitudes (job satisfaction and turnover intentions) and task performance. We examined both objective task performance quality and quantity to shed light on the complexity of the mindfulness–task performance relation, which has so far mostly been investigated using subjective supervisor ratings. In a sample of 174 blue‐collar workers in a Mexican company, results showed that employee mindfulness was negatively related to boredom. Further, mindfulness was positively related to job satisfaction and negatively to turnover intentions, partly mediated through boredom. Mindfulness turned out to be a double‐edged sword for task performance in monotonous jobs: Mindfulness was positively related to task performance quality but negatively related to quantity. Practitioner points In repetitive, monotonous jobs held by millions of people worldwide, more mindful employees perceive their job as less boring. Furthermore, mindful employees have higher job satisfaction and are less likely to quit. With regard to objective job performance, mindfulness can be a double‐edged sword: It positively affects objective performance quality via boredom, but negatively affects objective performance quantity directly.