Melanoma, an immunogenic tumor, is the first indication where oncolytic viruses are now becoming part of clinical practice. ONCOS-102, a transgened adenovirus, has shown to act as a primer of relevant tumor targeting immune cells both in preclinical and clinical melanoma studies. Strategies to augment its effectiveness warrant investigation. Combination therapy of ONCOS-102 with the checkpoint inhibitor (CPI) pembrolizumab was evaluated in a quasi-human animal model, the humanized NOG mouse model. A dosing schedule of the combination, beginning the CPI concurrently with the oncolytic viral therapy and continuing the CPI treatment, appeared to induce an abscopal effect in untreated tumor lesions. Concurrent combination therapy with checkpoint inhibitors may improve the induction of antitumor immune responses of ONCOS-102.