The human mitotic arrest-deficient 2 (Mad2) binding protein p31^comet participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31^comet as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31^comet, homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31^comet, together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31^comet and radiation sensitive 51c (rad51c) p31^comet double mutants, indicates that P31^comet plays an essential role in double-strand break (DSB) formation. Interestingly, the dynamic colocalization pattern between P31^comet and ZEP1 (a transverse filament protein of SC) by immunostaining, as well as the interaction between P31^comet and CENTRAL REGION COMPONENT 1 (CRC1) in yeast two-hybrid assays, suggests possible involvement of P31^comet in SC installation. Together, these data indicate that P31^comet plays a key role in DSB formation and SC installation, mainly through its cooperation with CRC1.