Patients with long-term health sequelae of COVID-19 (post-COVID-19 condition) experience both physical and cognitive manifestations. However, there is still uncertainty about the prevalence of physical impairment in these patients and whether there is a link between physical and cognitive function. The aim was to assess the prevalence of physical impairment and investigate the association with cognition in patients assessed in a post-COVID-19 clinic. In this cross-sectional study, patients referred to an outpatient clinic ≥ 3 months after acute infection underwent screening of their physical and cognitive function as part of a comprehensive multidisciplinary assessment. Physical function was assessed with the 6-Minute Walk Test, the 30 s Sit-to-Stand Test and by measuring handgrip strength. Cognitive function was assessed with the Screen for Cognitive Impairment in Psychiatry and the Trail Making Test-Part B. Physical impairment was tested by comparing the patients’ performance to normative and expected values. Association with cognition was investigated using correlation analyses and the possible explanatory variables regarding physical function were assessed using regression analyses. In total, we included 292 patients, the mean age was 52 (±15) years, 56% were women and 50% had been hospitalised during an acute COVID-19 infection. The prevalence of physical impairment ranged from 23% in functional exercise capacity to 59% in lower extremity muscle strength and function. There was no greater risk of physical impairment in previously hospitalised compared with the non-hospitalised patients. There was a weak to moderate association between physical and cognitive function. The cognitive test scores had statistically significant prediction value for all three outcomes of physical function. In conclusion, physical impairments were prevalent amongst patients assessed for post-COVID-19 condition regardless of their hospitalisation status and these were associated with more cognitive dysfunction.