The Fc region of immunoglobulin G (IgG) contains a conserved N-linked glycan at Asn297; its structural variations significantly influence interactions with Fc gamma receptors (FcγRs). Recently, glycoengineering technologies have progressed substantially, allowing precise control over glycan structures and enabling the development of antibodies with enhanced effector functions. This review outlines the biological significance of Fc glycosylation, recent advances in glycoengineering strategies, and their applications, including our own findings. Although the pair of N-glycans present in the Fc region of antibodies is structurally heterogeneous in most cases, previous methods for antibody glycan remodeling have been limited to the generation of symmetric structures. We discovered that IgG can be separated according to the number of Fc glycans through FcγRIIIa affinity column chromatography. By adding second glycans to the isolated hemi-glycosylated IgG, we developed a method to produce IgG molecules that possess structurally distinct paired glycans while maintaining glycan homogeneity at each site. Antibody–drug conjugates (ADCs) have demonstrated remarkable antitumor activity in clinical settings and numerous efforts are underway to develop improved formats. To broaden the therapeutic window, site-specific conjugation strategies are attracting increasing attention as alternatives to conventional random conjugation methods. By expanding antibody glycoengineering approaches, we established a site-specific conjugation platform that enables the generation of structurally homogeneous ADCs exhibiting the anticipated cytotoxic effects to antigen expressed cells.