The condensin complex forms a ring around chromosomes during mitosis and meiosis, which is important for their proper segregation. Here, the authors investigate how these defects arise, and show that induced cleavage of the condensin ring causes cells to arrest in metaphase of the next cell cycle, owing to the induction of a DNA damage-dependent checkpoint. Fluorescent microscopy imaging of chromosomes showed that experimentally induced cleavage of the condensin ring led to accumulation of DNA double-strand breaks during cytokinesis, but this did not prevent completion of cell division. Remarkably, induction of condensin ring re-closure shortly before anaphase was sufficient to rescue chromosome arm segregation. Thus, the condensin ring protects chromosome arms against damage induction during cytokinesis, and thereby ensures proper chromosome segregation.