The tendon of the flexor carpi radialis muscle is a fibrous structure that transits in its own compartment, lateral to the carpal canal or in a different path, superficial to the carpal tunnel. Its clinical importance is associated with osteoarthritis, tenosyvititis, tendinopathies and surgical interventions with potential iatrogenic injuries are frequent. However, its topography is described predominantly in the carpus of adult individuals in a controversial way, with few descriptions in children. The available studies are focused on a clinical approach and there are no studies on the anatomy of the flexor carpi radialis muscle tendon describing its course and limits in children. Thus, a description of the tunnel that contains the tendon becomes relevant, considering its anatomical characteristics in children, as well as the establishment of a specific nomenclature for the structure, since it is not included in the current anatomical nomenclature. Therefore, the present study aims to describe the morphology and morphometry of the tendon tunnel of the flexor carpi radialis muscle in children using dissection, magnetic resonance and histomorphometric methods, in samples of 33 hands of children aged 2 to 11 years old, without gender identification, from the Laboratory of Human Anatomy of the Department of Structural and Functional Biology of the Institute of Biology at UNICAMP. The samples used were from the Doctoral Research Project entitled Anatomical and histomorphometric bases for the understanding of median and ulnar nerve neuropathies in children, which has already been concluded. The current, complementary study will provide subsidies for the understanding of the development of the flexor radial muscle tendon tunnel and its location, as well as for the establishment of precise anatomical references for imaging diagnosis and for the surgical approach to the carpus.