Abstract: Safety-critical systems (e.g., UAV systems) often incorporate warning modules that alert users regarding imminent hazards (e.g., system failures). However, these warning systems are often not perfect, and trigger false alarms, which can lead to negative emotions and affect subsequent system usage. Although various feedback mechanisms have been studied in the past to counter the possible negative effects of system errors, the effect of such feedback mechanisms and system errors on users’ immediate emotions and task performance is not clear. To investigate the influence of affective feedback on participants’ immediate emotions, we designed a 2 (warning reliability: high/low) × 2 (feedback: present/absent) between-group study where participants interacted with a simulated UAV system to identify and neutralize enemy vehicles under time constraint. Task performance along with participants’ facial expressions were analyzed. Results indicated that giving feedback decreased fear emotions during the task whereas warning increased frustration for high reliability groups compared to low reliability groups. Finally, feedback was found not to affect task performance.