<p>Background: Perceived social support is a variable highly relevant for the health-disease process. Thus, it is crucial to have available valid and reliable measures for measuring it. Therefore, we aimed to determine the psychometric properties of the ENRICHD Social Support Instrument, in both a sample of undergraduate and a sample of adults. Moreover, we sought to determine whether the scale is invariant between men and women. Method: Two non-probabilistic samples were studied. Sample 1 was comprised of 538 undergraduate, and sample 2 collected data from 446 adults. Exploratory Factor Analyses, Confirmatory Factor Analyses, and internal consistency were conducted. A multigroup confirmatory factor analysis was performed testing for invariance among men and women. Results: The scale reliability was excellent in both samples. A single factor was confirmed in both undergraduate and adults. The scale is metrically invariant. Conclusions: ESSI is a reliable and valid scale. Its single factor structure is metrically invariant among men and women, and Its small number of items, suggests that this scale can be used for measuring the perceived social support reliably and validly, in both undergraduate and adults’ people.</p>