The study has produced a single, powerful finding: the fish value chain in Bangladesh is growing and transforming very rapidly, in all segments. (1) The quiet revolution in the fish value chain is a domestic market revolution: 94% of aquaculture production is destined for domestic consumption. (2) The farmed fish market grew by a factor of 25 times in three decades to nearly 2 million tons today. At most 10% of farmed fish are home-consumed, the rest are marketed. 42% of marketed farmed fish is consumed in urban areas and that share is growing fast. (3) There has been a tripling of volumes and actors in all the segments of the value chain over the past decade. (4) There has been rapid capital deepening in the form of investments by hundreds of thousands of actors in the fish value chain; apparent in a great jump in feed use, investment in equipment and pond construction, and investments in mills, hatcheries and vehicles. These investments have been made by, and provided opportunities for, a multitude of smallholder farmers and small and medium enterprises throughout the chain. (5) There has been diversification and specialization beyond carps into production of commercial species such as tilapia and pangasius catfish, which have raised yields and helped to move the fisheries sector along the “product cycle.” (6) So far the quiet revolution is driven by increase in demand, improvement in infrastructure, and investments by small-scale actors apart from large feed mills. Very little change is due to imposition of standards and contracts, or NGO or government action (except initial government support at the earliest stages in the 1980s). The most important policy has been infrastructure investment, good business environment, and laissez faire policy in terms of crop choice of farmers. Statement of relevance: This study focuses on the transformation of aquaculture in Bangladesh, a dynamic sector that has been driven by investments of hundreds of thousands of mainly small actors in the fish value chain. Investments that have bolstered the diversification beyond the production of carps, into production of new commercial species, raising yields and then reducing the price of consumed fish over time.