The current research examines the impact of four independent diversity variables, gender, age, educational background, and ethnicity, on the moderating role of diversity beliefs and the mediating role of leadership expertise to measure organisational performance in Pakistan. A self-administered questionnaire using a 6-point Likert scale approach was adopted to collect the responses from 176 employees. Quantitative analysis was done using SPSS, and SMART-PLS3 were used for was used to comprehend the objectives of the research. The findings indicate that age diversity, diversity beliefs, and leadership expertise have a statistically significant impact on organisational performance. Moreover, moderating variable diversity belief did not affect organisational performance, but leadership expertise plays a significant mediating role in organisational performance. Our study provides critical theoretical contributions to research diversity and organisational performance in Pakistan and examines the impact of workforce diversity on organisational performance with leadership expertise as mediator and diversity beliefs as a moderator.