© 2018 Elsevier Ltd Emerging evidence points to interactions between inflammatory markers and stress reactivity in predicting mental health risk, but underlying mechanisms are not well understood. Macrophage Migration Inhibitory Factor (MIF) is a pleiotropic cytokine involved in inflammatory signaling and Hypothalamus Pituitary Adrenal (HPA) axis stress-response, and has recently been identified as a candidate biomarker for depression and anxiety risk. We examined polymorphic variations of the MIF gene in association with baseline MIF levels, HPA axis reactivity, and self-reported anxiety responses to a social stressor in 74 adolescents, ages 10–14 years. Genotyping was performed for two polymorphisms, the -794 CATT5-8 tetranucleotide repeat and the -173*G/C single nucleotide polymorphism (SNP). Youth carrying the MIF-173*C and CATT7 alleles displayed attenuated cortisol reactivity when compared with non-carriers. Children with the CATT7-173*C haplotype displayed lower cortisol reactivity to the stressor compared to those without this haplotype. Additionally, the CATT5-173*C and CATT6-173*C haplotypes were associated with lower self-reported anxiety ratings across the stressor. Results extend prior work pointing to the influence of MIF signaling on neuroendocrine response to stress and suggest a potential pathophysiological pathway underlying risk for stress-related physical and mental health disorders. To our knowledge, these are the first data showing associations between the MIF gene, HPA axis reactivity, and anxiety symptoms during adolescence.