Previous studies have assessed the relative effect of instructional supervision, psycho-social and professional support on teacher’s job performance in secondary or higher education. Little or nothing is yet to be known about the effect of these variables on teacher’s job performance at the primary education level. This study is the first to show the relative and cumulative effect of instructional supervision, psycho-social and professional support on teacher’s job performance in primary education. An ex-post facto research design was adopted for the study, with a sample of 965 teachers selected through the proportionate stratified sampling technique. Two instruments – the “Improvement Strategies Questionnaire (ISQ)” and the Teachers’ Effectiveness Scale (TES) were used for data collection. Findings showed a significant effect of all the independent variables partially and jointly on the job performance of primary education teachers. Based on this conclusion, policy implications are discussed, while it is recommended amongst others, that headteachers in primary school should ensure that they visit classrooms regularly to monitor the teaching activities of teachers. This would enable them (headteachers) to identify teachers with sound, average or weak pedagogical skills for service delivery; professional counsellors should be recruited and deployed to all primary schools to cater for the psychological and social needs of teachers and pupils; regular retraining programmes on the ethics of teaching should be organised for teachers from time to time to enable primary education teachers to acquire skills in line with the changing society.