Most organizations have been reporting their inability to achieve the set objectives. Several factors have been pointed out to be the major cause. Apart from other external factors such as adequate finance, political goodwill and conducive environment, there seem to be other factors related to the intergroup cohesion that affect goal achievement. This study was done in schools in Lang’ata Sub County and it sought to establish the intergroup cohesion on employee performance in public schools in Lang’ata Sub County. The study had three objectives, to access how intergroup cohesion affects members’ commitment during performance of duties, to examine the effects of intergroup cohesion on task performance and to evaluate various effects of training on employee performance. It focused on employees who were be selected purposefully. After the study, it was found that intergroup cohesion and its aspects like training, commitment and workload affect employee performance. This implies that intergroup has a lot of effects when it comes to employee’s performance and that there is need to improve the team cohesion if we were to enjoy the benefits of teamwork. The study recommends that; there is need for institutions to have a strategic plan to enable it work towards a certain goal while committing themselves in work. This will help employees to remain focused to a certain goal and remain committed into realizing that goal or objective, there is need for institutions to have a well laid program that guides on how tasks should be administered to each group in an organization and need for institutions to take into consideration the new trends in job performance and bring in resource persons who will help train the members for better productivity. Finally, that there is need for institutions to have an elaborate plan which will work towards improving cohesion if maximum performance is to be realized.