The study set to determine the relationship between on-job training and employee turnover in the telecommunications sector in Kenya. Its objectives were: to investigate the kind of extant on-job training in Safaricom Ltd; to determine the effect of employee turnover after undergoing on-job training in Safaricom Ltd; to establish the factors motivating employees turnover after training in Safaricom Ltd and; to establish the relationship between on-job training and employees turnover in Safaricom Ltd. The null hypothesis adopted in this study was that there is no significant relationship between on-job training and employee turnover in Safaricom Ltd. This study used a case study research strategy. It targeted 67 employees of Safaricom Ltd. drawn from two job groups 4 and 5 through stratified proportionate sampling. A questionnaire shall be the only research tool used in this study. The findings obtained shall be presented in Tables and Figures. This study found that there on-job training, as is practiced in Safaricom Ltd. is important. As such, organizations need to invest in it. But as they do so, they should realize that it often leads to turnover. Turnover is caused by various factors. The most important factors include the need for high pay after training, competition from other organizations that might want the skills acquired by such employees after training, the need for promotion and better working conditions, and breach of psychological contract after training among others. When turnover occurs, organizations are affected in various ways. One of the major ways in which organizations are affected is loss of revenue, delay in realization of organizational goals, loss of competitiveness as well as loss of requisite skills. Lastly, the study established clearly that there is clear nexus between on-job training and employee turnover. Based on this, the following recommendations are made. The study recommends that managers should have a clear understanding of the influence of on-job training on employee turnover before embarking on such training. This is essential since it could enable employees to put in place ways of curbing the associated turnover. To this end, various measures can be put in place to check turnover put in place budgets to cater for increased pay; have measures for discouraging turnover, and; revise employment contracts to curb turnover among others. Training should also be well planned such that in the eventuality of turnover, companies can make up for such loss by getting suitable replacements. Furthermore, organizations can also avert the loss associated with a training-related turnover by employing persons who already possess the requisite skills.