Various solutions for handling data duplication with respect to user equipment and network apparatus in mobile communications are described. An apparatus may establish a first link and a second link with a network. The apparatus may generate a first protocol data unit (PDU) to transmit on the first link. The apparatus may generate a second PDU to transmit on the second link. The apparatus may transmit the first PDU on the first link. The apparatus may determine whether to discard the second PDU according to a condition. The second PDU may be duplicated from the first PDU.