Objectives: Studies involving simulators are increasingly popular. We examined to what extent exposure to a variety of test conditions on the simulator affects the level of mood and severity of simulator sickness. In addition, we were interested in finding out to what degree the changes in mood are associated with the severity of the symptoms of simulator sickness. Material and Methods: Twelve men (aged M: 29.8, SD: 4.26) participated in the study, performing two 30-minute tasks in a driving simulator truck (fixed-base and mobile platform). For measuring mood, the UMACL questionnaire was used, and to assess the severity of the symptoms of simulator sickness, the SSQ questionnaire was used. Mood and the severity of simulator sickness symptoms were measured 3 times during the study (pretest, 2 min and 0.5 h after the test). Results: Symptoms of nausea and disorientation occurred after the tests on both simulators. In the case of the mobile platform, exacerbation of the symptoms associated with oculomotor disturbances was observed. These symptoms were particularly severe 2 min after completion of the test on the simulator, and they persisted for at least 0.5 h after the end of the test. The correlations between simulator sickness and mood explained from 35% to 65% of the variance of these variables. In particular, a strong association was observed between the oculomotor disturbances and a decrease in energetic arousal. This refers both to the effect level and the duration of these symptoms. Conclusions: Simulator sickness is a major problem in the use of simulators in both the research and the training of operators. In the conditions involving the mobile platform, not only was a higher severity of the symptoms of simulator sickness observed, but also a decrease in energetic arousal. Therefore, the implementation of the mobile platform can provide an additional source of conflict at the level of incoming stimuli and changes in mood may increase this effect. Thus, it seems important to consider the tasks performed on the simulator in the context of utility and the purpose for which we use them.