Objectives Interpersonal problems were examined as moderators of depression outcomes between mindfulness‐based cognitive therapy (MBCT) and cognitive behavioral analysis system of psychotherapy (CBASP) in patients with chronic depression. Methods Patients received treatment‐as‐usual and, in addition, were randomized to 8‐weeks of MBCT (n = 34) or 8‐weeks of CBASP (n = 34). MBCT and CBASP were given in a group format. The Hamilton depression rating scale (HAM‐D) was the primary and the Beck Depression Inventory (BDI‐II) the secondary outcome. The subscales of the Inventory of interpersonal problems (IIP‐32) were moderators. Multilevel models were performed. Results Higher scores on the “vindictive/self‐centered” subscale were associated with a better outcome in MBCT than in CBASP (HAM‐D: p < .01; BDI‐II: p < .01). Higher scores on the “nonassertive” subscale were associated with a better outcome in CBASP than in MBCT (HAM‐D: p < .01; BDI‐II: p < .01). Conclusions If these results can be replicated in larger trials, MBCT should be preferred to CBASP in chronically depressed patients being vindictive/self‐centered, whereas CBASP should be preferred to MBCT in chronically depressed patients being nonassertive.