Post-translational modification is an important mechanism to determine protein levels and/or activities in cells. The process of conjugation of ubiquitin units to particular proteins, ubiquitination, usually leads to proteasomal degradation. During the past several years considerable work has been done to reveal the role of ubiquitination in the regulation of plant signaling and development. This article focuses on recent advances made on the study of ubiquitin-mediated proteolysis of several light-related signaling pathways, such as photomorphogenesis, circadian clock function, and photoperiodic flowering.