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Drought has become one of the environmental threats to agriculture and food security. Applications of melatonin (MT) serve as an effective way to alleviate drought stress, but the underlying mechanism remains poorly understood. Here, we found that foliar spray of 100-µM MT greatly mitigated the severe drought stress-induced damages in rice seedlings, including improved survival rates, enhanced antioxidant system, and adjusted osmotic balance. However, mutation of the <i>suppressor of the G2 allele of skp1</i> (<i>OsSGT1</i>) and <i>ABSCISIC ACID INSENSITIVE 5</i> (<i>OsABI5</i>) abolished the effects of MT. Furthermore, the upregulated expression of <i>OsABI5</i> was detected in wild type (WT) under drought stress, irrespective of MT treatment, whereas <i>OsABI5</i> was significantly downregulated in <i>sgt1</i> and <i>sgt1abi5</i> mutants. In contrast, no change of the <i>OsSGT1</i> expression level was detected in <i>abi5</i>. Moreover, mutation of <i>OsSGT1</i> and <i>OsABI5</i> significantly suppressed the expression of genes associated with the antioxidant system. These results suggested that the functions of <i>OsSGT1</i> in the MT-mediated alleviation of drought stress were associated with the ABI5-mediated signals. Collectively, we demonstrated that OsSGT1 was involved in the drought response of rice and that melatonin promoted SGT1-involved signals to ameliorate drought stress adaption.