Lean, Six Sigma, and Theory of Constraints (TOC) are methodologies that focus on continuous improvement, that is why this paper presents one integrated system, where the three methodologies are combined simultaneously. The system is based on the five steps of TOC and used Lean and Six Sigma tools in order to identify the value flow in the process, by eliminating unproductive activities and controlling the variability of the critical process. The proposed system is applied in the furniture industry in Lima, Peru. The initial evaluation were accomplished using surveys and interviews. The results shows that Small Medium Enterprises (SME) have low productivity. In this case, an empirical model was used to validate the proposed methodology Six Sigma Theory of Constraints (6TOC). Based on this, it is possible to reduce production times and costs, which allows a 6% increase in productivity and raise the Sigma level in 4 of the SMEs that manufacture furniture in Peru. Finally, it can be said that 6TOC is a powerful tool that allows the wood furniture sector to achieve continuous improvement.