Antibody conjugates are used in many therapeutic and research applications and are generated by chemically linking a cysteine or lysine residue to potent chemotherapeutic drugs or other functional groups through a flexible linker. Recently, we have engineered THIOMABs (antibodies with engineered reactive cysteine residues) for site-specific conjugation and showed that these antibody conjugates display homogeneous labeling with optimal in vitro and in vivo characteristics. Here, we describe protocols for engineering, selection, and site-specific conjugation of THIOMABs with thiol-reactive linkers.