Background: Patients who are post-COVID-19 will require more treatment soon. Therefore, it is important to understand the root cause of their psychological and somatic conditions. Previous studies showed contradictory results on the influence of pre-existing mental conditions. The present study examines the influence of these pre-existing conditions and their pre-treatment on the severity of post-COVID-19 symptoms. Methods: This analysis employs questionnaire data from a large study sample in Germany. Overall, 801 participants were included. All participants rated their health status on a scale from 0 to 100. Fatigue, depression, and anxiety were measured using the FAS, PHQ-9, and GAD-7 scales. Results: All pre-pandemic values showed no significant differences between the groups. The current health status was rated similarly by the recovered patients (μ = 80.5 ± 17.0) and the control group (μ = 81.2 ± 18.0) but significantly worse by acutely infected (μ = 59.0 ± 21.5) and post-COVID-19 patients (μ = 54.2 ± 21.1). Fatigue, depression, and anxiety were similar for recovered patients and the control group. By contrast, there were significant differences between the control and the post-COVID-19 groups concerning fatigue (45.9% vs. 93.1%), depression (19.3% vs. 53.8%), and anxiety (19.3% vs. 22.3%). Conclusion: Fatigue and psychological conditions of post-COVID-19 patients are not associated with pre-existing conditions.