Provided herein are, inter alia, antibodies capable of binding Structural Maintenance of Chromosome-1 (SMC1). The antibodies provided herein include novel light chain and heavy chain sequences and bind SMC1 (e.g., SMC1A or SMC1B) with high efficiency and specificity. The SMC1 antibodies provided herein including embodiments thereof may be used for diagnostic and therapeutic purposes, for example, as humanized SMC1 antibodies, antibody drug conjugates or they may form part of bispecific antibodies or chimeric antigen receptors.