|Abstract||The application of VSM is a proven approach for lean-based improvements. Typically, this becomes challenging, when applied for complex production environments. The purpose of this research is to demonstrate, how with some approximations and simplifications in VSM application, lean can be successfully achieved in these environments. The research follows case study method and systematically guides about the segregation and treatment of non-value-adding(NVA) and value-adding (VA) activities of heavy-duty industrial power transformer making process. The focal company operates in engineer to order (ETO) and high-mix low-volume (HMLV) environments. With a research team using gemba walks and systematic questioning technique, relevant data were collected for mapping. Taguchi method was also applied for one of the critical steps, which was influencing cycle time and energy requirements. The generalisable findings endorse the strengths of approach for lean by addressing wastes and cycle time reduction. The study establishes that VSM application-based lean messages remain same for both simple and complex environments. It also exposes that non-compliance of VSM assumptions' and micro-concepts' are the root causes for application complexities. The study also offers useful insights and practical guidelines to facilitate lean in ETO, construction and HMLV production environments.