A method for performing seamless transmission control for an electronic device and an associated apparatus are provided, where the method includes the steps of: sending a request frame carrying a fragment identification (ID) to trigger a responder in a wireless network system to initiate retransmission corresponding to the fragment ID, wherein the fragment ID indicates beginning of a remaining portion within a plurality of fragments of data being sent from the responder to the electronic device; and receiving at least one response frame sent from the responder, for utilizing the remaining portion within the plurality of fragments of the data, wherein the remaining portion within the plurality of fragments of the data is obtained from the at least one response frame.