This study assessed the influence of leadership styles on organisational effectiveness of selected public universities in Uganda. Specifically, the study assessed the influence of transformational, transactional and laissez-faire leadership styles on organisational effectiveness. The study used the correlational research design on a sample of 93 respondents that were university managers, namely administrative and academic heads of Busitema and Kyambogo Universities in Uganda. Data was collected using a self-administered questionnaire and analysed using quantitative methods that were descriptive and partial least squares structural equation modelling (PLS-SEM) with the help of SmartPLS. Descriptive results revealed that organisational effectiveness, the use of transactional and laissez-faire leadership styles were moderate while the use of the transformational leadership style was high. SEM results indicated that while the transformational and transactional leadership styles had a significant positive influence on organisational effectiveness, the laissez-faire leadership style had a positive but insignificant influence on organisational effectiveness. It was, therefore, concluded that the transformational leadership and transactional leadership styles are imperative for organisational effectiveness of public universities but the laissez-faire style is not. The study recommended that university leaders should emphasise the use of the transformational and transactional leadership styles to enhance organisational effectiveness. However, university leaders should minimise the use of the laissez-faire leadership style. The significance of this study is that it identifies leadership styles that are necessary for enhancing organisational effectiveness.