This paper analyzes the impact of corporate governance on family business performance. Moreover, the study tries to verify whether the relationship between corporate governance and performance varies in periods of instability. We consider a sample of all Portuguese-listed firms on Euronext Lisbon, excluding financial companies and sports clubs, for the period between 2010 and 2023, using the generalized method of moments estimation to account for endogeneity in panel data analysis. The results show that gender diversity positively impacts firms’ performance in the cases of accounting performance measures and that smaller boards are associated with higher levels of accounting and market performance measures. Concerning the impact of CEO duality on performance, our results suggest conflicting effects according to the performance measures, since it shows a negative relationship between duality and the return on assets, but a positive relationship in the case of the return on equity and Tobin’s Q measure. Moreover, periods of instability have a significant adverse effect on performance. Firms’ age, leverage, and economic growth impact on companies’ performance. The results show evidence that corporate governance characteristics are determinants of firm performance, and highlight the conflict between agency and stewardship theories, suggesting the need for context-sensitive governance choices.