Various solutions for handling packet data convergence protocol (PDCP) duplication with respect to user equipment and network apparatus in mobile communications are described. An apparatus may determine whether a PDCP entity is associated with two radio link control (RLC) entities. The apparatus may determine whether PDCP duplication is activated. The apparatus may select one of the two RLC entities to transmit a PDCP control protocol data unit (PDU) in an event that the PDCP entity is associated with the two RLC entities and the PDCP duplication is activated.