High levels of reactive oxygen species (ROS) in and around maturing oocytes lead to oxidative stress, which decrease fertilization success rates. Melatonin reduces levels of ROS during in vitro fertilization in swine. The objective was to determine the effects of melatonin during oocyte maturation on: IVF kinetics and embryonic development. Oocytes (n = 50/well) were supplemented during the last 24 h of maturation with 0, 75, 100, or 150 nM melatonin and then subjected to IVF and embryo culture. Frozen-thawed semen from a single boar was used (approximately 30 oocytes/well, 200 sperm/oocyte). A total of 600 oocytes over 3 replicates were used in this study with one well/ treatment/ replicate. Post IVF, a percentage of the embryos were evaluated for penetration, polyspermy, and male pronuclear formation rates. The remaining embryos were evaluated 48 h after IVF for cleavage and 144 h for blastocyst formation. Data were analyzed using ANOVA with the main effects including treatment, well and replicate. Chi-squared analysis was used to determine percentages of embryos reaching the different developmental stages for each treatment. There were no differences between treatment groups with respect to penetration and polyspermy. Supplementation of 150 nM melatonin produced a significant (P < 0.05) percent of embryos with MPN (25. 93 ± 21.17%) compared with those supplemented with 75 nM (66.67 ± 21.17%) or 100 nM (79.17 ± 21.17%). There was no difference between the 75 nM and 100 nM treatment groups. Supplementation of 150 nM (22.00 ± 21.37%) produced significantly (P < 0.05) less of cleavage between all of the other treatment groups 48 h after IVF. Embryo supplementation of 75 nM melatonin during maturation had significantly higher (P < 0.05) percentage of blastocyst formation by 144 h after IVF compared with those supplemented with 150 nM (10.00 ± 17.32%) of melatonin. There was no difference in the percent of embryos reaching the blastocyst stage of development by 144 h after IVF between no supplementation, 100 nM, and 75 nM of melatonin. These results indicate that the supplementation of 75 nM melatonin during the later stages of maturation improves embryo development by increasing cleavage and blastocyst rates 48 and 144 h after IVF, respectively.