The impact of leaders' integrity on organisations and employees' effectiveness has not been thoroughly studied, possibly due to the absence of a comprehensive measurement scale in this domain. Recognizing this gap, the current study aimed to develop the Perceived Leaders' Integrity Assessment Scale (PLIAS). Specifically, the scale assesses employees' perception of their leader's integrity, where the leader is defined as the employee's current employer (i.e., immediate supervisor/manager). For this purpose, data were collected from (N=1,430) employees in Pakistan. In Phase I, phenomenology (i.e., integrity, honesty, ethics, and supportive behaviour) was studied, a pool of items was generated, and 40 items were screened. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were applied in Phase II, and five factors for the PLIAS, including ethical, immoral, unethical, supportive, and positive attitudes, were identified. In Phase III, psychometric validation. These suggest that the PLIAS is a reliable tool for assessing the perceived integrity of leaders by employees of their current employer (i.e., immediate supervisor/manager). Overall, developing and validating the PLIAS dramatically enhances the understanding of leadership characteristics in workplace settings. By providing a standardized instrument for assessing leaders' integrity, the PLIAS enables organisations to gain insights into the impact of leadership integrity on employee effectiveness and organisational outcomes.