In today's highly competitive world where most businesses focus on cost and quality, organizations with efficient and effective supply chains are able to stand out with inherent competitive advantages. To achieve this many organizations adopt lean practices which fundamentally stress on the elimination of non-value added tasks (such as unwanted transportation, extra processing, excess motion, repairs on defects, over production, excess inventory and incidents of waiting or delays). Nevertheless, the introduction of lean practices in any organization is often accompanied by changes in the working environment. These changes influence the people working there. This study looks into the perceptions of the workers, in a case study site (a Japanese Multi-National Corporation situated in Penang, Malaysia producing semi-conductor devices), on the lean practices implemented in the internal supply chains. The study compared the perceptions using a self-administered questionnaire. Perceptions of those highly exposed to lean practices were compared against the perceptions of those with low exposure. A significant difference, in the perceptions of those who had high exposures to lean practices as compared to those with low exposures pertaining to the internal supply chain performances, was found. The perceptions obtained proved useful as empirical studies showed negative implications such as the deteriorations in employee emotions, attitudes, behaviors, commitments and turnovers. Moreover, the perceptions of the employees and the employers also did not match. Useful recommendations have been put forth which could be used for improving the internal supply chain performances of other organizations. The recommendations encompass areas such as resource allocations, mind-set changes, trainings, personnel and lean practice implementation strategies.