Standard psychological treatment of obsessive-compulsive disorder (OCD) typically involves the behavioural-based therapy exposure and response prevention (ERP). This study compared the effectiveness of ERP with the recently developed cognitive therapy-based treatment package, Danger Ideation Reduction Therapy for obsessive-compulsive checkers (DIRT-C) (Vaccaro, Jones, Menzies, and St Clare). Both treatments were delivered in 14 1-hr individual weekly sessions. Post-treatment intention-to-treat analysis revealed large statistically significant improvements for participants in both ERP (n = 22) and DIRT-C (n = 28) conditions. However, treatment effect sizes for change in OCD symptom severity at post-treatment were greater for DIRT-C than for ERP (3.74 versus 2.89). In addition, at post-treatment assessment, significantly more participants who received DIRT-C were recovered compared with those who received ERP (43% versus 14%). Similarly, at 6-month follow-up, treatment effect sizes for change in OCD symptom severity were greater for DIRT-C than for ERP (3.9 versus 2.76). This study provides further evidence of the usefulness of the DIRT-C package for people with OCD checking subtype. Future research investigating DIRT-C is warranted.