The branched-chain amino acids (BCAAs) leucine, isoleucine, and valine are synthesized by bacteria, fungi, and plants, but are essential for vertebrates including humans, who must receive them from their diet. The interest to construct overproducing industrial strains therefore stems from the need to supplement the food or feed with these amino acids to use them in medical treatment and as precursors in biochemical synthesis. Regulation of the biosynthesis pathways of branched-chain amino acids has many features, such as homologous reactions catalyzed by a single enzyme, branching of the pathways and multivalent regulation of both gene expression and enzyme activity, which make their analysis both interesting and challenging. The structural similarity of these three amino acids and their precursors causes their alternative binding to the proteins as substrates, inhibitors, activators, and passengers in transporters with different affinities. Studies of threonine deaminase, the first enzyme specific for isoleucine biosynthesis, and of acetohydroxyacid synthase, the first common enzyme in the pathways of BCAA biosynthesis, promoted the discovery of feedback inhibition and may serve as paradigms for this regulatory mechanism. Regulation of the Escherichia coli operons ilvGMEDA and ilvBN provides examples of typical translation-mediated transcriptional termination (attenuation). Mechanisms of regulation by the seemingly similar structures found in ilvBNC operon and leuA gene of the industrial amino acid producer Corynebacterium glutamicum still have to be unveiled. A wide range of different specific and global regulatory mechanisms being gradually uncovered in various microorganisms will contribute to the knowledge of genetic control of BCAA biosynthesis.