This study sought to determine the influence of recognition benefits on medical employees output at Kenyatta National Hospital (KNH) as moderated by workers ‘union activities. The study was guided by Reinforcement theory. The study employed both descriptive and explanatory research design and pragmatism philosophy. The target population of the study comprised of 2175 employees drawn from Kenyatta National Hospital. Stratified and purposive sampling techniques were used to select a representative sample of 328 respondents. The primary data for the study was collected using closed ended questionnaires and structured interview schedule. Quantitative data was analyzed using both descriptive statistics (frequencies, percentages, means, standard deviation) and inferential statistics (Regression, Correlation and ANOVA). The findings indicated that recognition programs had a positive and significant relationship with employee output at KNH. It was also established that workers’ union activities significantly moderate the relationship between recognition programs and employee output among medical employees at KNH. The study concludes that recognition programs enhance employee output in hospitals. In addition, under high level of worker union activities, recognition programs had a positive and significant relationship with employee output at KNH. The study recommends that organizations need to work towards recognizing their staff appropriately so that they can exhibit improved employee output.