Previous research has raised concerns that scores derived from the Personality Inventory for DSM–5 (PID-5; American Psychiatric Association, 2013; Krueger, Derringer, Markon, Watson, & Skodol, 2012) may be compromised by response styles such as underreporting or overreporting. The informant-report form of the PID-5 (PID-5-IRF; Markon, Quilty, Bagby, & Krueger, 2013) has been recommended for use when response bias is an assessment concern. The purpose of the current investigation was to evaluate PID-5 and PID-5-IRF scale score elevations across participants exhibiting signs of overreporting or underreporting. A total of 245 adults completed the PID-5 and the Revised NEO Personality Inventory (NEO PI-R; Costa & McCrae, 1992). A family member or friend of at least 1 year’s acquaintance completed the PID-5-IRF for 216 of these. A total of 211 target-informant pairs were available for analysis. Participants were categorized as overreporting and underreporting according to NEO PI-R validity scale cutoffs. The majority of PID-5 scale scores were elevated in those identified as overreporting; more than half of the PID-5-IRF scale scores were similarly elevated. The majority of PID-5 scale scores were lower in those scoring above underreporting cut-offs; however, PID-5-IRF scales were not as consistently or strongly impacted. PID-5 scales were strongly impacted by response bias, whereas PID-5-IRF scores were less strongly impacted overall, and more so by overreporting bias. Caution when using these instruments in the assessment of personality disorders prone to over- or underreporting may be warranted.