Background: Internet use is pervasive in many cultures. Little is known about the impact of Obsessive-Compulsive Personality Disorder (OCPD) symptoms on impulsive and compulsive psychopathologies in people who use the Internet. Method: 1323 adult Internet users completed an online questionnaire quantifying OCPD symptoms, likely occurrence of select mental disorders (OCD, ADHD, problematic Internet use, anxiety), and personality questionnaires of impulsivity (Barratt) and compulsivity (Padua). Predictors of presence of OCPD symptoms (endorsement of at least 4 of 8 DSM criteria) were identified using binary logistic regression. Results: In regression (p<0.001, AUC 0.77), OCPD symptoms were significantly associated with (in order of decreasing effect size): lower non-planning impulsivity, higher ADHD symptoms, problematic Internet use, avoidant personality disorder, female gender, generalized anxiety disorder, and some types of compulsions (checking, dressing/washing). Conclusions: These data suggest that OCPD symptoms, defined in terms of at least 4 of 8 DSM tick-list criteria being met, are common in Internet users. OCPD symptoms were associated with considerably higher levels of psychopathology relating to both impulsive (ADHD) and compulsive (OC-related and problematic Internet use) disorders. These data merit replication and extension using gold-standard in-person clinical assessments, as the current study relied on self-report over the Internet.