Oncolytic viruses (OVs) are designed to selectively infect, proliferate within, and destroy cancer cells while concurrently eliciting robust antitumor immune responses. Notwithstanding their significant potential, inadequate tumor selectivity and restricted treatment efficacy persist as substantial barriers to wider clinical utilization. This review rigorously evaluates current advancements in OV engineering designed to address these issues. Transcriptional targeting, which employs tumor-specific promoters like hTERT, E2F1, and hypoxia-inducible elements, microRNA detargeting, and the redirection of viral entry towards tumor-associated antigens such as EGFR, HER2, and EpCAM, alongside multi-layered logic-gated regulatory systems, represent strategies to augment tumor specificity. To bolster anticancer efficacy, OVs have been modified with immunomodulatory agents, including cytokines (GM-CSF, IL-12), immune checkpoint inhibitors (anti-PD-1, anti-CTLA-4), chemokines, and stroma-degrading enzymes (hyaluronidase, relaxin). Subsequent advancements encompass nanoparticle encapsulation, carrier-cell transport mechanisms, metabolic reprogramming strategies, and synergistic combinations with immunotherapy, chemotherapy, or radiotherapy. Furthermore, systems and synthetic biology techniques are enabling the development of advanced "smart" OVs, which possess the capacity for real-time detection and adaptation within the tumor microenvironment. These combined methodologies present considerable promise for enhancing the safety profile, intratumoral distribution, and overall therapeutic efficacy of oncolytic virotherapy.