This research finds evidence for reliable individual differences in people’s perceived attitude stability that predict the actual stability of their attitudes over time. Study 1 examines the reliability and factor structure of an 11-item Personal Attitude Stability Scale (PASS). Study 2 establishes test–retest reliability for the PASS over a 5-week period. Studies 3a and 3b demonstrate the convergent and discriminant validity of the PASS in relation to relevant existing individual differences. Studies 4 and 5 show that the PASS predicts attitude stability following a delay period across several distinct topics. Across multiple attitude objects, for people with high (vs. low) scores on the PASS, Time 1 attitudes were more predictive of their Time 2 attitudes, indicative of greater attitudinal consistency over time. The final study also demonstrates that the PASS predicts attitude stability above and beyond other related scales.