The halogenated borophene is theoretically found to exhibit excellent performance in metal-oxide-semiconductor field-effect transistors (MOSFETs) benefiting from the anisotropic electronic structure. In consideration of the thermal management of MOSFETs, the thermal transport mechanisms in halogenated borophene need to be explored. In this work, with the combination of first-principles and phonon Boltzmann transport equation, we report disparate in-plane thermal anisotropy in halogenated monolayer B