This study tested whether high spider fearful individuals’ implicit and explicit attitudes toward spiders are sensitive to exposure treatment, and whether post-treatment implicit and/or explicit attitudes are related to the generalization of treatment effects. Self-reported explicit and implicit attitudes (indexed with a pictorial Extrinsic Affective Simon Task) were assessed in high spider fearful, treatment-seeking individuals (n = 60) before and after a one-session exposure in vivo treatment and at 2-month follow-up. A group of non-fearful participants (n = 30) completed the same assessments once. Results show that implicit attitudes did not change following treatment over and above test–retest effects. In contrast, explicit attitudes did change favorably following treatment, but negative explicit attitudes at post-treatment were associated with less pronounced overt approach behavior at follow-up. These findings support the idea that residual negative explicit attitudes interfere with the generalization of treatment effects.