Abstract Background : There is a consensus that receiving satisfactory social support is crucial for elderly people experiencing chronic pain; however, no instruments have been validated for the Cuban population. The Medical Outcomes Study (MOS) is an instrument that has been widely validated across several countries, indicating significant psychometric properties to measure perceived social support; however, MOS has never been applied to Cubans. This study obtained evidence of the internal and external validity of the original MOS survey structure and its brief 8-item version in a sample of Cuban seniors with chronic pain. Methods : The sample included 200 Cuban single and retired seniors, with an intermediate level of education. The MOS Social Support Survey and a structured interview were conducted to obtain socio-demographic information and learn about the support perceived by elders in pain. A confirmatory factor analysis (CFA) was used to test the structure. Cronbach’s alpha and omega coefficients were considered for internal consistency, in addition to the relation between the item variance and error variance (Average variance extracted). Furthermore, Spearman’s rho coefficient was used to estimate the correlations between the MOS scores and the support assessment given by seniors in pain. Results: All the models assessed through the CFA indicated good adjustment indices. However, the brief version of the model gave better results. Of the coefficients assessing internal consistency, the 2-factor 8-item version indicated the best indicators and accounted for greater variance not attributable to the error. Both versions of the MOS and their corresponding sub-scales obtained significant positive correlations with the support received by seniors in pain. Conclusions: The MOS (4-factor) and the 8-item brief version (with 2 factors) present suitable evidence of structural validity, internal consistency, and external validity.