This research study examines the effect of employees’ involvement in decision making on organization performance with the mediating role of organization culture. Primary data was collected for evaluating the consequence, sources of data was employees of operational level of telecommunication industry (PTCL) operating in Islamabad, probability random sampling technique was used, sample size was generated by sample size calculator and data was collected from 270 employees working at operational level through close ended questionnaire. Data was statistically analyzed by indicating regression analysis. Statistical analysis showed that there was positive relation between employee involvement in decision making and organization performance, and there is a significant role of organization culture in encouraging and showing the effectiveness of employees’ involvement on organization performance. In order to increase organization performance, management has to focus more on employees’ involvement concept that will positively affect employees’ commitment and satisfaction, and the growth of better organization performance. Supervisor:- Prof. Dr. Usman Mustafa