Continuous Improvement (CI) is a core dimension of Total Quality Management grounded in W. Edwards Deming’s Theory of Profound Knowledge, which emphasizes system optimization, process control, and incremental improvement through the Plan–Do–Check–Act (PDCA) cycle. In the competitive tea industry of Kenya’s South Rift Region, multinational tea companies have increasingly adopted continuous improvement initiatives to enhance product quality, operational efficiency, and overall organizational performance. However, variations in performance outcomes raise questions regarding the extent to which continuous improvement practices translate into measurable organizational gains. This study examined the effect of continuous improvement on the performance of multinational tea companies in the South Rift Region, Kenya, guided exclusively by Deming’s systems-based philosophy. Anchored on a positivist paradigm and correlational research design, data were collected from 222 middle- and top-level managers selected through stratified random sampling from a population of 499 respondents. Structured questionnaires were used, and data were analyzed using descriptive and inferential statistics, particularly linear regression analysis. Reliability of the instrument was confirmed (Cronbach’s α = 0.814), and diagnostic tests verified compliance with classical regression assumptions. The findings revealed that continuous improvement had a positive and statistically significant effect on organizational performance (β = 0.644, p < 0.05). The results indicate that practices such as process optimization, regular employee training, incremental innovation, and quality enhancement significantly improve productivity, efficiency, and competitiveness of multinational tea firms. The study concludes that embedding continuous improvement within organizational systems, as advocated by Deming’s Theory of Profound Knowledge, is critical to achieving sustained performance outcomes in the tea sector.