Research supports that anorexia nervosa-restricting subtype (AN-R) and bulimia nervosa (BN) are associated with emotion regulation difficulties and alexithymia. However, the impact of diagnosis on the relationship between these constructs is less well understood. The purpose of the present study was to examine whether eating disorder diagnosis moderated the association between admission alexithymia and emotion regulation through discharge. Adult patients with AN-R (n = 54) and BN (n = 60) completed assessments at treatment admission and discharge from a partial hospital program. Eating disorder diagnosis moderated the association between admission alexithymia levels and change in global emotion dysregulation, impulse control difficulties and access to emotion regulation strategies. At higher levels of admission alexithymia, there were no differences between AN-R and BN on emotion dysregulation, whereas at lower levels of alexithymia, AN-R patients demonstrated lower levels of emotion dysregulation. Results imply that difficulties with alexithymia appear to have a greater impact on emotion dysregulation for AN-R patients. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.