Purpose Supported by the literature on dynamic capabilities, this study aims to propose a moderated mediation model to examine how entrepreneurial alertness advances new firm performance by identifying strategic flexibility as a pivotal mediator and absorptive capacity as a crucial contingency. Design/methodology/approach This paper collects data from 137 new firms regarding activities that were considered essential during the COVID-19 contingency in Mexico. The hypotheses are tested using hierarchical multiple regression analysis, complemented with the bootstrapping approach to confirm the indirect and conditional effects of entrepreneurial alertness on firm performance through strategic flexibility. Findings The results yielded general support for the study hypotheses, suggesting that entrepreneurs’ alertness facilitates the firms’ ability to respond to changes in their context, namely, strategic flexibility; strategic flexibility enables firms make useful changes, leading to better performance; entrepreneurial alertness indirectly affects new firm performance through strategic flexibility; absorptive capacity has a positive moderating impact on the entrepreneurial alertness-strategic flexibility relationship; and the positive influence of entrepreneurial alertness on strategic flexibility and ultimately new firm performance was increased in high rather than in low absorptive capacity. Practical implications This study highlights that entrepreneurs’ cognitive mechanisms shape the behaviour of their firms through strategic decisions. This paper studies the influence of entrepreneurs’ alertness on strategic flexibility, examines the interplay between entrepreneurial alertness and environmental conditions via absorptive capacity and proposes a moderated mediation model to understand the effect of entrepreneurs’ alertness on strategic flexibility and new firm performance. Originality/value The study investigates the influence of assertive message framing and individual value orientations on the reactance process in the context of environmentally friendly mobility. It finds individual value orientations to be a significant factor in the reactance process, further extending the psychological reactance theory. Moreover, it revalidates reactance as a construct consisting of anger and negative cognition.