This study investigated the impact of workforce engagement on performance of Manufacturing Firms in Kisii County. The study sought to ascertain the ascertain the impact of job security on employee job satisfaction of Manufacturing Firms in Kisii County, assess the effect of rewards and recognition on employee output of Manufacturing Firms in Kisii County, examine the influence of involvement and participation on effectiveness of Manufacturing Firms in Kisii County and analyze the factors affecting workforce engagement on performance of Manufacturing Firms in Kisii County. This research adopted a survey design. This study adopted two sources of data collection which are primary data and secondary data. The population of the study was 237 staff. Thus, the sample size was 149 which were distributed to the respondents in the study area. One hundred and thirty nine (139) were returned while ten (10) were rejected. The researcher used a simple random sampling technique. ANOVA, correlation coefficient and regression model was used to test hypotheses of the study. The study found out that Job security has a significant effect on employee job satisfaction of Selected Manufacturing Firms in Kisii County. Rewards and recognition has a significant impact on employee output of Selected Manufacturing Firms in Kisii County. Involvement and participation has a significant effect on effectiveness of Selected Manufacturing Firms in Kisii County. The study concluded that Ineffective communication and inefficiency at work are the challenges affecting workforce engagement on performance of Selected Manufacturing Firms in Kisii County. The study recommended that organization should hold to high esteem effective communication and job security as a satisfactory form of appreciation that will stop employee thinking about other opportunities from other organization.