Various examples and schemes pertaining to an AT-command for an always-on PDU session in mobile communications are described. A processor of an apparatus implemented as a user equipment (UE) establishes a protocol data unit (PDU) session between a modem of the apparatus and a network node of a wireless network in response to a trigger by an application executed on the processor. The processor forwards a query from the application to the modem for an indication provided by the network node on whether the established PDU session is an always-on PDU session. The processor then receives the indication provided by the network node from the modem.