Apparatus and methods are provided to reduce mobility interruption time through dual-protocol stacks for mobility enhancement. In novel aspect, the UE configures a target protocol stack for a target gNB upon receiving a reconfiguration message from a source gNB, performs random access procedure and establishes RRC connection with the target gNB through the target protocol stack while simultaneously maintaining data transmission and reception with the source gNB, and releases the source RRC connection with the source gNB and performs data transmission and reception with the target gNB upon detecting one or more predefined release triggering event. In one embodiment, the target protocol stack includes a PHY layer, a MAC layer, and RLC layer, a PDCP and optionally a SDAP. In one embodiment, the UE enables a PDCP reordering, wherein the PDCP reordering is performed on PDCP packet data units received from the source and the target protocol stacks.