Pigeonpea [Cajanus cajan (L.) Millsp.], also known as redgram, is one of the major grain legume (pulses) crops grown in the semiarid tropics (SAT) extending between 30 degrees N and 30 degrees S; it is the second most important food legume of India. It is cultivated in about 50 countries of Asia, Africa, and the Americas for a variety of uses (food, fodder, fuel wood, rearing lac insects, hedges, wind breaks, soil conservation, green manure, roofing, and so on). The constraints of enhancing its productivity include the damage caused by various fungi, bacteria, viruses, and insect pests. Conventional plant breeding methods have not been successful for the improvement of pigeonpea because of genetic variation and incompatibility among the wild varieties. Genetic engineering technology can therefore be used as an additional tool for the introduction of agronomically useful traits into established varieties. The development of plant transformation techniques has been a major breakthrough in overcoming constraints to achieve precision in genetic manipulation. The development of efficient plant regeneration protocols is a prerequisite for recombinant technology to carry out genetic transformation. This chapter describes an Agrobacterium-mediated transformation protocol for pigeonpea, a simple, efficient, and reproducible method that is applicable across diverse genotypes of pigeonpea.