The present paper describes various Indigenous Technical Knowledge (ITK) of the fishermen community of Indian Sundarbans in West Bengal documented during the period from 2013 to 2015. A total of eleven ITKs were documented including therapeutic value of fish with special reference to small indigenous fishes (SIF) and were categorised based on their uses. Effectiveness and rationality were assessed based on the view of the experts as well as that of fishers. The study indicated that seven ITKs documented were rational and effective. Those valid ITKs include four types of unique fishing methods; fish as special energy booster; methods to support natural fish breeding and fish marketing. Remaining four ITKs, like use of fishes to address unique human health issues, method to reduce mortality during prawn seed transport and behaviour of fish for forecasting extreme climatic events, although appeared as irrational and less effective as per the view of experts, fishers are practicing them and hence demand special attention for proper validation, improvement and popularisation in the context of changing regional resource structure and stakeholders’ needs.