With the intention to analyze the effects of different board characteristics on the insurance companies’ performance, this research article explores the impact of board gender diversity and size on the performance of the insurance companies in Croatia. It analyzes the impact of characteristics of both boards, the board of directors and the supervisory board on corporate performance. The analysis, conducted using dynamic panel model, covers all insurance companies in Croatia operating in the 2007–2013 period. The main findings suggest that gender diversity at the top positions is not critical for financial success. Specifically, it is established that women acting as presidents of supervisory board deteriorate insurer’s performance measured by return on assets (ROA). This is also the case when more women are present in the board of directors. Moreover, the findings of the model measuring performance by both ROA and return on equity demonstrate that financial performance of insurance companies is negatively influenced by the number of members of the board of directors. The article upgrades the existing research by providing new support for the effects of board structure on performance in insurance industry, with specific reference to effects of gender diversity. Moreover, this study extends the existing literature in this field by introducing two corporate governance mechanisms in the analysis, that is, both the board of directors and the supervisory board. Furthermore, it is, to the authors knowledge, the first attempt to describe the effects of diversity in terms of gender on performance in the insurance sector.