Psychological flexibility (PF) is the core process set underlying Acceptance and Commitment Therapy (ACT) and appears to be fundamental to health and wellbeing. However, existing measures of PF are each limited in one or more important ways and further instrument development is needed. Post-COVID Condition (PCC) is a significant health condition that can include complex symptoms and substantially impacts on daily functioning and wellbeing, making it an ideal population for testing a measures of PF. The present study aimed to develop and validate the Comprehensive Flexibility Profiler (CFP), examine its psychometric properties in a Swedish PCC sample, and potential utility. Adult participants with self-reported PCC were recruited through online and via healthcare settings, and 431 valid responses were included (81.4% female; mean age = 53.9 years). Based on a 12-dimensional framework (flexibility: present moment attention, acceptance, values, cognitive defusion, committed action, self-as-context; inflexibility: lack of present attention, avoidance, lack of values, cognitive fusion, inaction, self-as-content), a 60-item instrument was developed. Exploratory factor analysis (EFA), confirmatory factor analysis (CFA), correlation analysis, and hierarchical regression were conducted to evaluate reliability and validity, and incremental validity was compared with an established measure of PF. The CFP total scale and subscales demonstrated good internal consistency (Cronbach’s α = 0.83-0.97). The first-order 12- factor CFA model showed good fit (CFI = 0.993, TLI = 0.992, RMSEA = 0.045). The bifactor model with one general higher‑order factor, attempting to accommodate the full set of 12 facets, failed to converge, whereas the separate single-sided bifactor models for flexibility and inflexibility both showed excellent fit. Correlation analyses indicated that CFP scores were associated with functional impairment (WSAS), depression (PHQ-9), and life satisfaction (SWLS) in the expected directions. Hierarchical regression analyses showed that, after controlling for demographic variables and relevant general psychological variables (anxiety and insomnia when predicting depression; anxiety, depression, and insomnia when predicting functional impairment and life satisfaction), the flexibility total score remained as a significant predictor of functional impairment (ΔR² = 2.0%), life satisfaction (ΔR² = 4.8%), and depression (ΔR² = 4.1%). At the facet level, present moment attention was negatively associated with functional impairment and depression, values was positively associated with life satisfaction, and inaction was positively associated with functional impairment and depression. Compared with the Psy-flex, the CFP demonstrated significant incremental associations across all outcome measures (additional explained variance = 3.3%-4.2%). The CFP shows good reliability and validity in the sample of people experiencing persistent symptoms post COVID-19 and appears promising for further studying this population.