This study investigates the determinants of growth of companies listed on the Johannesburg Securities Exchange. The literature on firm growth has identified numerous determinants of growth, demonstrating that growth is a multidimensional and complex phenomenon. The factors identified, however, have often yielded contradictory results regarding their influence, primarily since the operationalisation of growth relies on several approaches in terms of measures or periods retained. This study focuses on firm-specific determinants, which include firm size, firm age, gender diversity, liquidity, leverage, and profitability. The dependent variable, firm growth, was measured using the logarithmic difference in total sales. The data were collected from the INET BFA (IRESS) database and published annual reports. Using panel data of 187 companies listed on the Johannesburg Securities Exchange (JSE) during the period 2009–2018, the fixed-effect results show that firm growth, liquidity, and profitability are negatively correlated with firm growth. The results further reveal that the law of proportionate effect or Gibrat’s law is not valid for JSE-listed companies since a positive and significant relationship between firm size and firm growth was found in this research. Moreover, gender diversity and leverage were found to have no significant effect on the growth of JSE-listed companies.