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In this study, ultrahigh-performance concrete (UHPC) was utilized in precast segmental beams to reduce the self-weight, shorten the construction time, and improve the performance and durability of bridges. Owing to the discontinuity in the joints, shear behavior plays a critical role in the overall structural performance of precast UHPC segmental beams (PUSBs). Therefore, four dry-jointed segmental specimens along with one monolithic specimen were designed and tested under a two-point concentrated load with various joint types, shear span-to-depth ratios (λ), and numbers of shear keys. Two types of shear failure modes were observed in the tests: shear compression failure of the web (λ = 1.44 and 2.56) and local shear failure of the flanges at the joint (λ = 3.67). The shear capacity, stiffness, and cracking load of the dry-jointed segmental specimens were lower than those of the monolithic specimen, and the single-keyed specimen exhibited better shear behavior than the three-keyed specimen. Increasing λ decreased the shear strength and stiffness of the segmental beams and considerably affected their failure modes and crack distributions. Additionally, four UHPC design codes were evaluated for their accuracy in estimating the shear strength of the specimens, and a simplified strut-and-tie model was developed to predict the shear strength of externally pre-stressed PUSBs. Finally, several design recommendations were proposed. This study is expected to facilitate the research and application of PUSBs. [ABSTRACT FROM AUTHOR]