The effect of thermo-hygro-mechanical (THM) densification temperature on the surface color, roughness, wettability, and chemical composition of trembling aspen (Populus tremuloides) and hybrid poplar (Populus maximowiczii×P. balsamifera) veneers was investigated. Veneers were subjected to four THM densification temperatures (160°C, 180°C, 200°C, and 220°C). Veneer color darkened with increasing THM densification temperature. Surface roughness decreased between 160°C and 200°C. Wettability decreased after THM densification, but no significant difference was found between treated specimens. ATR-FTIR and XPS results confirmed that THM densification caused major chemical changes in veneer surfaces, and more pronounced at temperatures higher than 160°C.