Embodiments of this application provide an information transmission method, an apparatus, and a system. A first network device sends, to a terminal device, conditional handover configuration information that includes information about candidate cells and a handover trigger condition; after receiving the conditional handover configuration information and performing a conditional handover, the terminal device sends, to a second network device, a first failure cause value corresponding to a candidate target cell and/or a second failure cause value corresponding to a to-be-determined cell during the conditional handover; and the second network device receives the first failure cause value and/or the second failure cause value from the terminal device, and sends the first failure cause value and/or the second failure cause value to the first network device.