The purpose of the study was to assess human resource planning on organisational behaviour and performance, using the Ghana Education Service as case study. The researcher used descriptive research design for the study. The objectives of the study were to establish the relationship between human resource planning and organisational performance, to identify the strategies use to improve human resource planning and to assess the challenges faced by an organisation in human resource planning. Quantitative research approach was used. The population for the study consists of all the human resource directors and staff of G.E.S Ashanti Region. The main instrument used to gather primary data was questionnaire. The computer statistical package for social scientists (SPSS version 20) was used to analyses data. The study indicates that human resource planning helps in assessing and recruiting skilled human resource. It again revealed that HRP helps in creating g and sustaining organizational performance and competitive advantage. The study, again, revealed that there is a positive significant relationship between human resource plan and organisational performance. It was also concluded that evaluation of human resource planning has a relationship with fulfilling the objectives of manpower requirement. The study recommended that the planning Unit for Human Resources of GES should also involve the employees in the plans they make so that they feel part of the GES and also this would prepare them in case of any change.HUMAN RESOURCE PLANNING ON ORGANISATIONAL BEHAVIOUR: A CASE OF GHANA EDUCATION SERVICE, GES, KUMASI METROPOLIS.