Herpes simplex virus type 1 (HSV-1) is a DNA virus with strong replication capabilities, a large genomic payload (≥30 kb), and low toxicity, making it a prominent vector in cancer gene therapy. Clinically approved oncolytic HSV-1 (oHSV-1) variants, such as T-VEC and G47Δ, demonstrate safety and efficacy in localized tumors, but face challenges in treating metastatic disease. To address this issue, next-generation oHSV-1 designs focus on precision targeting and immune remodeling through the delivery of multiple exogenous genes. In this review, we provide an overview of the inherent characteristics of oHSV-1 as a gene delivery platform, focusing on its genetic modification strategies, safety challenges in clinical applications, and future directions to maximize its therapeutic potential.