Methods and apparatus for private network peering in virtual network environments in which peerings between virtual client private networks on a provider network may be established by clients via an API to a peering service. The peering service and API 104 may allow clients to dynamically establish and manage virtual network transit centers on the provider network at which virtual ports may be established and configured, virtual peerings between private networks may be requested and, if accepted, established, and routing information for the peerings may be specified and exchanged. Once a virtual peering between client private networks is established, packets may be exchanged between the respective client private networks via the peering over the network substrate according to the overlay network technology used by the provider network, for example an encapsulation protocol technology.