Various embodiments are generally directed to implementing a secure mailbox in resource-constrained embedded systems. An apparatus to establish communication with a trusted execution environment includes a processor component, a co-processor component for executing the trusted execution environment, a host operating system component for execution by the processor component and including one or more application components, a mailbox array component for execution by the co-processor to store one or more mailbox components, each mailbox component being associated with a mailbox identification number, and a mailbox firewall component for execution by the co-processor component to facilitate communication between the one or more application components and the one or more mailbox components. Other embodiments are described and claimed.