This study explores the mediating role of self-undermining in the relationship between job insecurity and employee outcomes in the higher education sector. Using data from 4743 participants across ten countries, we examined how quantitative and qualitative job insecurity affect in-role performance and counterproductive work behaviors through self-undermining behaviors. The results indicate that quantitative job insecurity negatively impacts in-role performance and promotes counterproductive work behaviors, with self-undermining serving as a mediator in these relationships. Conversely, qualitative job insecurity exhibits a complex relationship, showing both positive and negative effects on performance and behaviors, mediated by self-undermining. These findings underscore the importance of addressing job insecurity and self-undermining to enhance employee performance and reduce counterproductive behaviors in academic settings. Practical implications and directions for future research are discussed.