This study determined the effect of workplace safety ergonomics on employee productivity in manufacturing firms in Kenya. The study was grounded on the domino theory. The study adopted a cross-sectional survey research design, guided by positivist research philosophy. The target population was 853 manufacturing firms that were registered with the Kenya Association of Manufacturers (KAM). A sample of 124 firms distributed across the fourteen sub-sectors in the manufacturing sector was obtained. The target respondents were 124 heads of human resources in each sampled firm. Data was collected using structured questionnaires. Regressions analysis was used. The results established that workplace safety ergonomics in the form of hazard detectors, protective devices and effects analysis have a statistically significant influence on the productivity of employees in manufacturing firms. The findings offer insight into the significance of safety ergonomics on employees’ value added, degree of accomplishment of tasks and productive time.