There are both positives and negatives to constructing high-rise buildings in high population densities of large cities. The negative effect of oppressiveness ( 圧迫感 ) will be the focus of this paper. Oppressiveness is defined as the negative feeling resulting from being surrounded by high-rise buildings. Building oppressiveness when combined with other urban stresses contributes towards making compact cities unsustainable. In other words these negative psychological factors of the environment are barriers to achieving urban sustainability. Therefore it is important to find ways to mitigate the negative psychological effects of high-rise buildings in order to improve the benefits of compact cities. This research assesses the psychological effect of green building façades and trees in Tokyo while taking into consideration a real urban environment. Within the context of the goal of "Green Urbanism" this research also measures and compares the effect of these two different types of greenery on residents' psychology. The methodology consisted of two experiments that were conducted in the Hongo area of downtown Tokyo. The aim was to assess the effects of green façades and trees in terms of environmental psychology and compare them. The results showed that the effect of greenery on the façade of buildings is not as positive as the effect of a tree-lined street. Trees are significantly more effective in mitigating the perception of oppressiveness. The results are important for urban designers and government policy makers.