<p>The exponential growth of e-commerce over the last years is changing people’s shopping and mobility, with sustainability implications. Most contributions explore the substitution or complementarity effects of e-commerce by analyzing people’s shopping trips, but customer behavior in the counterfactual scenario (non-availability of e-shopping) has not been addressed. This paper provides interesting insights by studying mobility and shopping behavior if e-commerce had not been available through a survey data analysis, taking the Region of Madrid (Spain) as the case study, with more than 1,300 valid observations. The research calibrates a Generalized Structural Equation Model (GSEM) to analyze e-shopping habits and associated mobility at the individual level, both in actual and counterfactual shopping behavior, and study the influence of multiple explanatory variables: socio-demographics, mobility patterns, e-shopping behavior (delivery characteristics and mobility), and psychological and lifestyle preferences. According to the results, more than half of the e-purchases corresponded to products available close to home, while only a minority of them were induced (products that would not otherwise have been purchased). E-shopping behavior, residential location (urban vs suburban) and lifestyle attitudes (e.g., environmental consciousness) emerge as key drivers in determining the substitution or complementarity effect of e-shopping and its resulting implications on mobility. In view of the modelling results, the paper discusses the impact (positive or negative) that e-commerce may have on sustainability depending on the spatial context. Finally, it proposes recommendations to make e-commerce more sustainable.</p>