Viral vectors are essential substances for gene therapy, which is still developing. Through them, gene therapy becomes a reality for both inheritable and non-inheritable diseases. Molecular cloning and vector construction, combined with early investigations into retroviruses, have formed a foundation for stable gene delivery. Lentiviral expression systems have been developed to facilitate gene delivery in non-dividing cell types and for use in immuno-oncology. Due to improvements in capsid design, targeting, and safety, the adeno-associated virus (AAV) has become the primary in vivo platform for gene therapy. Besides cancer therapy and vaccines, other viral platforms such as adenovirus, herpes simplex virus, vaccinia virus, measles virus, and Newcastle disease virus have been introduced. The first clinical achievements are represented by the approved gene therapies for hemophilia, retinal degeneration, and immunodeficiency disorders. While immune responses, limited transgene capacity (load), and issues with targeted delivery still pose challenges, the use of viral vectors as gene delivery vehicles in therapeutic applications has been confirmed by these trials. Additionally, oncolytic viruses, as well as viruses used as vectors to induce immunomodulatory effects, present new possibilities for cancer immunotherapy. Additionally, the researchers are exploring novel clinical applications of oncolytic viruses for the treatment of neurological disorders and metabolic diseases. Additionally, the combination of oncolytic viruses with technologies such as gene editing and neuromodulation represents another potential source of therapeutic expansion. Although limited applications in standard clinical practice have been demonstrated in recent years, this field of research has been rejuvenated by new scientific discoveries, clinical applications involving human subjects, and increased funding for the development of viral vectors in the treatment of various diseases. It seems that viral vectors are going to be instrumental in the molecular medicine of the next stage.