Example methods are provided a first host to perform packet flow monitoring in a software-defined networking (SDN) environment. One example may comprise the first host receiving a request to monitor a packet flow and triggering a telemetry process based on a predetermined event associated with the packet flow. The method may also comprise: in response to the triggered telemetry process and detecting an egress packet associated with the packet flow, generating an encapsulated packet by encapsulating the egress packet with an outer header; configuring a telemetry instruction in the outer header; and sending the encapsulated packet with the telemetry instruction to the second host via one or more intermediate network devices. The telemetry instruction may be configured to cause the one or more intermediate network devices to add, to the encapsulated packet, metadata associated with a network state experienced by the encapsulated packet.