© 2018 Wolters Kluwer Health, Inc. All rights reserved. Background:Treatment adherence and viral suppression remain suboptimal in the United States. Attachment insecurity may be one understudied factor affecting adherence. According to attachment theory, people develop generalized internal working models of interpersonal relationships, which shape their perceptions of the availability of others at times of stress and how they handle stressors as an individual. Two dimensions of attachment insecurity are attachment-related avoidance (avoidance of intimacy with others and avoidance of negative emotions) and attachment-related anxiety (feeling unable to deal with stressors without others' help). For people living with chronic stressful health conditions that require life-long self-management, attachment-related avoidance and attachment-related anxiety may diminish the ability to cope with stressors as an individual leading to negative health outcomes.Methods:We examined cross-sectional associations of the 2 attachment-related insecurity dimensions with antiretroviral treatment (ART) adherence, HIV visit adherence, CD4 cell counts, and viral suppression. Survey and clinical data from 453 women living with HIV in 4 US cities were analyzed controlling for age, education, income, time on ART, illicit drug use, and race.Results:Attachment-related avoidance was the only unique predictor of suboptimal ART adherence, viral failure, and low CD4 count, and attachment-related anxiety was the only unique predictor of missed HIV care visits. These effects were over and above the effects of all covariates. ART adherence mediated the association of attachment-related avoidance with both viral failure and low CD4 counts.Conclusions:Interventions may need to focus on the vulnerable subpopulation with high attachment insecurity and incorporate existing strategies that address insecure attachment models.