Prior research has shown that the combination of assessment and locomotion regulatory modes leads to the best performance-related outcomes. The aim of the current study was to analyse how familiarity and complexity moderate this relationship between the two regulatory modes and job performance. Participants' locomotion and assessment tendencies were measured, and they were asked to rate the familiarity and complexity of their daily work tasks, as well as their job performance over the last year. Results showed that when job tasks were unfamiliar and more complex, high locomotion and high assessment were both needed for optimal performance. However, when both familiarity and job complexity were low, high locomotion alone led to the best performance. A similar result was obtained when task familiarity was high: regardless of task complexity, the best performance was shown by employees high in locomotion, no matter the assessment. In conclusion, the present study furnishes useful suggestions for employers who wish to maximize employees' performance.