Purpose: The purpose of this study was to establish the influence of collaborative planning on performance of pharmaceutical firms in Kenya Methodology: This research adopted a descriptive research design. The target population of interest in this study were the 22 local pharmaceutical manufacturing and 149 importing firms that act as subsidiaries making a total of 171. The study sample was drawn from the list of 171 pharmaceutical firms, where various categories with the relevant information for the study were drawn. The study adopted a census sampling technique. Two questionnaires were administered to each firm to categories of people with relevant information about collaborative planning giving a total of 342. These included procurement officers, general managers, line managers or marketing managers. The data was analyzed using SPSS 22 version by making use of multiple regressions analysis which helped to generate a weighted estimation equation (OLS) that was used to predict values for dependent variable from the values of the independent variable. Results: The correlation and regression results revealed that collaborative planning had a positive and significant relationship with performance of pharmaceutical firms. The null hypothesis was rejected which indicated that there was a significant relationship between collaborative planning and performance of pharmaceutical firms in Kenya. Recommendations: The study recommends that management in pharmaceutical firms should promote and cultivate a culture which allows collaboration with their customers. This should be geared towards a model of Collaborative Planning Forecasting and Replenishment (CPFR) for successful supply relationships that enhance performance. This is because collaborative planning has been confirmed to have positive and significant effect on firm performance. The firms are therefore recommended to adopt collaborative planning through ways such as joint execution schedules, forecasting present and future needs, Replenishments, involving customers in joint project teams, involving them in new product development and planning as well as having an integrated IT systems. With this, the performance is deemed to improve.