Cell and gene therapies (CGTs) are redefining the treatment landscape for cancer and degenerative diseases by enabling precise, often durable, modulation of cellular function and immune responses. Regenerative medicine, driven largely by stem-cell–based approaches, focuses on restoring tissue structure and function in the context of injury, degeneration, or chronic inflammation. Integrating cell–gene immunotherapy with regenerative strategies offers a synergistic paradigm: engineered cells can both eliminate pathogenic or malignant elements and support functional tissue repair in the same therapeutic concept. This article reviews current platforms in immunogene therapy, including chimeric antigen receptor (CAR) T and natural killer (NK) cells, in vivo gene editing, and viral and non-viral delivery, alongside major regenerative modalities such as mesenchymal stromal cell (MSC) therapies and tissue-engineered constructs. Mechanistic intersections, including immune modulation, niche restoration, and cross-talk between inflammatory and regenerative signaling, are discussed in the context of oncology, neurodegeneration, and organ failure. Key translational challenges are analyzed, encompassing heterogeneity of response, manufacturing and cost, long-term safety, and regulatory–reimbursement misalignment. Finally, a conceptual roadmap is proposed for designing next-generation synergistic CGT–regenerative combinations, including rational target selection, trial design, and data-infrastructure requirements to support long-term follow-up.