Psoriasis and atopic dermatitis are relatively common in clinical practice, but it is rare for the two diseases to co-occur in the same patient. Dupilumab, an anti-IL-4/IL-13 monoclonal antibody, has been approved for treating moderate to severe AD. In addition to its therapeutic effects, dupilumab may induce new cutaneous adverse reactions. We report a rare case of pustular psoriasis induced during the treatment of atopic dermatitis with dupilumab. This case demonstrates the need for caution while treating patients with moderate to severe atopic dermatitis and staying vigilant for the emergence of new symptoms, especially with biological agents.