During development， Shh attracts commissural axons toward the floor plate through a non-canonical， transcription-independent signaling pathway that requires?the receptor Boc. Here， we find that Shh induces?Boc internalization into early endosomes and that endocytosis is required for Shh-mediated growth-cone turning. Numb， an endocytic adaptor， binds to Boc and is required for Boc internalization， Shh-mediated growth-cone turning in?vitro， and commissural axon guidance in?vivo. Similar to Boc， Ptch1 is also internalized by Shh in a Numb-dependent manner; however， the binding of Shh to Ptch1 alone is not sufficient to induce Ptch1 internalization nor growth-cone turning. Therefore， the binding of Shh to Boc is required for Ptch1 internalization and growth-cone turning. Our data support a model where Boc endocytosis via Numb is required for Ptch1 internalization and Shh signaling in axon guidance. Thus， Boc acts as a Shh-dependent endocytic platform gating Ptch1 internalization and Shh signaling.