Urban trees could provide a variety of ecosystem services. However, they require conservation to sustain a healthy and consistent provision of services. This study applies an extended theory of planned behavior (ETPB) to understand residents’ pay intention for conserving urban trees. In order to explore the impact of the public perception of urban trees, two constructs such as perceived usefulness and perceived tree benefits have been added to the TPB model. This study conducted a questionnaire survey on Taipei city residents and received 364 valid responses. The partial least squares structural equation modeling (PLS-SEM) was used for the analysis of the model. The results show that residents’ perceived usefulness and perceived tree benefits of urban trees have a significantly positive impact on public attitude toward protecting urban trees. Individuals’ intention to pay towards conservation of urban trees is, on the other hand, affected by subjective norm, attitude, perceived behavioral control, and perceived usefulness. Thus, with education and promotion of tree usefulness and benefits of ecosystem services, it is helpful to improve residents’ attitudes regarding the protection of urban trees and increase their intention to pay for urban tree conservation.