The development of eco-friendly connection material instead of steel is a chal- lenging problem in timber structures. Following densification, the mechanical properties of low-density species can be significantly improved. Densified wood may be a potential connection material in timber structures. This paper reviewed the different processing for densified wood, and obtained favorable mechanical properties and dimensional stability based on small specimen sizes, which are much less than the applicable sizes in practice. A densification pro- cessing with alkali pretreatment was adopted for poplar widely cultivated in the world to produce the densified poplar, which has been rarely reported as connection material. Various specimens of densified poplar were tested to obtain their main mechanical properties such as strength and deformability. The set recovery of densified poplar was also measured to observe their dimensional stability. In addition, the hygroscopic swelling strains for the diameter of den- sified poplar dowel were measured to present their moisture-dependent behavior. The improved mechanical properties and dimensional stability con- firmed the fact that densified poplar with alkali pretreatment can be an optimal connection material.