In the face of growing demand for local products, farmers are developing direct sales. Our research examines the impact of this strategy on farms' sustainability. Focusing on the market gardening sector, we compare metropolitan France and its overseas departments: Martinique, Guadeloupe and Reunion. These insular economies must meet national and European requirements for healthy and local production while complying with specific organizational and geographic conditions. If direct selling is considered an innovation, we first identify the factors, such as characteristics of farmers and their farm, determining its adoption. While establishing the link between such an innovation and performance, we study the impact of direct sales on farms' sustainability, inspired by the IDEA method. We use representative farm data from 2010 and 2016 and perform a propensity score matching coupled with a difference-indifference analysis. While the impact of direct sales on sustainability is effective in metropolitan France, more nuanced results are observed in insular economies. Whatever the location, direct sales provide a response to consumers' expectations in terms of product diversification. While direct sales are initially associated with product processing and tourism, these activities are gradually abandoned, in particular because of the skills necessary to their realization. In metropolitan France, direct selling modifies the relationship with certifications by developing organic production to the detriment of other types of certification. It is also accompanied by output and employment growth. Our results question the role that the environment in which farmers evolve plays in the sustainability dynamics of farms in island economies.