Background: Long COVID is a major manifestation of long-lasting symptoms experienced by the survivors of the coronavirus infection that may influence patients’ physical and mental health. Objectives: This study aimed to evaluate the association of the physical symptoms of COVID-19 (fatigue, breathlessness, and pain) and the level of physical activity with the physical and mental health of survivors in the post-COVID-19 period. Methods: This was a cross-sectional study conducted on 152 hospitalized and non-hospitalized adults infected with COVID-19 aged between 18 and 65 years at the post-infection period with follow-up times greater than 6 months. Standardized instruments, such as the SF12, International Physical Activity Questionnaire (IPAQ), Multidimensional Fatigue Inventory (MFI-20), and visual analog scale (VAS), were used for measuring pre-and post-COVID-19 painful symptoms, fatigue, and breathlessness. The severity of the coronavirus infection was judged based on hospitalization or ICU admission. Data were analyzed with linear regression analysis. Results: The results showed that, at a mean duration of 6 months post-discharge, only fatigue was associated with lower physical (F = 2.84, explained variance = 15.3%) and mental health (F = 1.88, explained variance = 10.6%) Conclusions: Considering the negative impact of fatigue on the physical and mental health of patients during the post-COVID period, it is suggested to monitor and manage fatigue for a longer period post-COVID-19.