<title>Abstract</title>
African blackwood (ABW: <italic>Dalbergia melanoxylon</italic>) is a valuable tree in Tanzanian local community forests, and heartwood has been mainly utilized as an irreplaceable material in musical instruments, e.g., clarinet, oboe and piccolo. Since its use is generally for the production of musical instruments only, most of the harvested volume is wasted due to defects that would affect the quality of final products. Wood flow forming can transform bulk woods into materials in temperature/pressure-controlled mold via plastic flow deformation. The main object of this study was to evaluate the deformation characteristics of ABW heartwood in developing the potential of wasted ABW parts in terms of the effective material use. The deformation characteristics of heartwood were examined by free compression tests. Specimens were compressed along the radial direction at 120 °C, and air-dried heartwood was dramatically deformed in the tangential direction. The plastic flow deformation of ABW was amplified by the presence of both extractives and moisture. In particular, the ethanol/benzene (1:2, v/v) soluble extractives in heartwood may have contributed to flow deformation. The results of the dynamic mechanical analysis showed that the air-dried heartwood exhibited softening in a temperature range over 50 °C. The ethanol/benzene-soluble extractives contributed to the softening behavior. The clarified deformation characteristics of ABW can contribute to more efficient material use of local forests.