In one embodiment, distributed path computation elements (PCEs) collaboratively build local portions of an inter-domain P2MP path to each path destination or to each ingress border router of one or more respective successor domains based on a cost associated with using one or more local ingress border routers received from each predecessor domain. Once a furthest destination is reached, each PCE may recursively return a list of local ingress border routers used in the P2MP path to each predecessor domain, where each PCE receiving the list correspondingly prunes segments of its computed local portion of the P2MP path that lead to unused successor ingress border routers, and sends a prune message to its predecessor domains accordingly. A root PCE receives the final prune message(s) and a representation of each locally computed portion of the inter-domain P2MP path, and combines the portions into a final inter-domain P2MP path.