To evaluate the contribution injection anxiety to disease modifying therapy (DMT) adherence among individuals with multiple sclerosis (MS). Injection anxiety has been associated with medication discontinuation early in the course of treatment, but little is known about the relationship between injection anxiety and sustained DMT adherence over time. Eighty-nine outpatients receiving care at a Veterans Administration MS clinic completed a telephone survey at baseline and monthly telephone follow-up for 6 months. Participants were established DMT users (M = 3.43 years, SD = 3.29), with relatively high adherence overall (over 80% achieved 80% adherence or greater). Using logistic regression and controlling for demographics, MS disability, type of DMT, and time on DMT, the authors found that baseline injection anxiety predicted lower levels of adherence at 4 months and 6 months, with a similar trend at 2 months. Sustained adherence to DMT remains a challenge for a subset of individuals with MS well beyond the initial period of acclimation. Injection anxiety is an important and promising target of psychological intervention during all periods of medication use.