Technologies for secure I/O with an external peripheral device link controller include a computing device coupled to an external dock device by an external peripheral link, such as a Thunderbolt link. The external dock device includes an I/O controller that receives device data from an I/O device, generates a channel identifier associated with the I/O device, and transmits I/O data that includes the channel identifier to a dock controller. The dock controller encapsulates the I/O data to generate peripheral link protocol data and transmits the peripheral link protocol data to a host controller of the computing device over the external peripheral link. The host controller de-encapsulates the peripheral link protocol data and forwards the I/O data to memory. The channel identifier may be a predetermined value associated with the I/O controller, or may include a controller identifier associated with the host controller. Other embodiments are described and claimed.