Purpose The aim of this study was to examine the psychometric properties of the Spanish version of the Experience of Caregiving Inventory (ECI-S), which is designed to assess the caregiver's appraisal of the impact of caring for a relative with a serious mental illness. Methods A cross-sectional study was conducted among 320 caregivers of a relative with an eating disorder to examine: (a) descriptive statistics; (b) internal consistency reliability; (c) the fit of the original ten-factor structure of the ECI through exploratory factor analysis, using a semi-confirmatory approach, for each subscale individually, and (d) concurrent validity. A total of 307 caregivers completed the scale. Results Reliability of the ECI subscales scores was acceptable (alpha = 0.63-0.89). Results replicated the original ten-factor structure of the instrument. The concurrent validity was supported by correlations of the ECI-negative subscale with psychological distress (GHQ-12, 0.43), and with depression and anxiety (HADS, 0.48 and 0.49, respectively). Conclusions The Spanish version of the ECI (ECI-S) demonstrated good psychometric properties in terms of validity and reliability that were similar to the original version. It is an acceptable and valid instrument for assessing the impact on family members of caring for a relative with an eating disorder and can be recommended for use in clinical settings in Spain.