CONSTANS-LIKE (COL) genes are important factors that play an important role in regulating photoperiod-dependent flowering time, and multiple COL genes have been identified in plants. However, knowledge of the COLs involved in photoperiod-dependent flowering time regulation is limited in mungbean (Vigna radiata). In this study, we characterized the function of VrCOL1 in regulating flowering time. VrCOL1 shares strong homology to the well-studied Arabidopsis AtCO and soybean GmCOL1a and GmCOL1b. VrCOL1/GmCOL1a and VrCOL1/GmCOL1b were demonstrated as two syntelogs, respectively. Subcellular localization analysis revealed that VrCOL1 is located in the nucleus. The expression of VrCOL1 increased under short-day (SD) conditions during growth phases, and the expression of VrCOL1 decreased under long-day (LD) conditions during growth phases. Overexpression of VrCOL1 accelerated flowering in Arabidopsis thaliana under SD conditions by activating the expression of FLOWERING LOCUS T (AtFT) and TWIN SISTER OF FT (AtTSF), whereas VrCOL1 had no effect on flowering time under LD conditions, indicating that VrCOL1 is involved in flowering time regulation under a photoperiod-dependent pathway. The results of our study provide new insights into the molecular mechanism of flowering time regulation in mungbean.