The study sought to determine the effects of internal control system and organizational performance in post bank. Internal controls were looked from the perspective of internal control environment, monitoring and control activities. The study selected one senior manager in their finance department. The researcher administered a survey questionnaire to each of the target population since it was the most appropriate tool top gather information. quantitative analysis and qualitative data analysis were used as data analysis technique. descriptive statistics such as mean, standard deviation and frequency distribution was done by use of tables for ease of understanding and interpretation. From the findings the study concludes that control environment, monitoring and control activities had a positive relationship with the organizational performance of post bank. the study found out that a unit increase in control environment would lead to increase in organizational performance of post bank, and further a unit increase in control activities would lead to increase in organizational performance. the study recommends that management in post Bank should adopt effective internal control systems such as such as control environment, monitoring and control activities to enhance organizational performance of post bank Kakiri branch. Post Bank should implement a monitoring system that influences organizational performance. This should be through carrying out effective monitoring, proper use of resources, a continuous performance monitoring process, review of staff performance, monitoring by teams and regular performance inspections.