This study aimed to analyse the influence of frugal innovation on the sustainability performance of Mexican SMEs and evaluate the moderating effect of firm size. A quantitative, predictive, and cross-sectional research design was carried out through Partial Least Squares Structural Equation Model (PLS-SEM). Using a simple random sampling technique and a self-administered questionnaire to gather data from a sample of 225 business managers in the state of Guanajuato, Mexico. The outcomes indicate that frugal innovation significantly contributes to sustainability performance. Moreover, the firm size plays a significant moderating role in the relationship between frugal innovation and sustainability performance, thus, when these types of firms achieve greater size, the relationship between frugal innovation and sustainability performance increases to the same extent as the size of the interaction.