Background Our aim is to evaluate the relationship between inspiratory muscle strength and venous refilling time, disease severity, and functional capacity in patients with chronic venous insufficiency (CVI). Methods Sixty-one patients (49 female, aged 20–65 ) were enrolled in the study. The demographic characteristics of the patients were questioned. All patients were assessed with maximum inspiratory and expiratory pressure (MIP/MEP) for inspiratory and expiratory muscle strength, photoplethysmography for venous refilling time (VRT), venous clinical severity score (VCSS) for disease severity, and 6-min walk test (6-MWT) for functional capacity. Results The mean age of the patients was 49.48 ± 13.19 years, and the mean duration of disease was 9.18 ± 6.57 years. There was statistically significant positive association between MIP and VRT(r: 0.331, p: 0.009), 6-MWT (r: 0.616, p < 0.001) values, and there was negative association between MIP and VCSS(r: -0.439 p < 0.001) scores. Conclusion Evaluation of inspiratory muscle strength and elimination of its deficiency, providing interventions to approach normative values have the potential to contribute positively to the treatment of the patient.