Interleukin-12 (IL-12) is considered to be a promising cytokine for enhancing anti-tumor immune response. However, recombinant IL-12 had significant toxicity and limited efficacy in early clinical trials. Recently, many strategies for delivering IL-12 to tumor tissues have been developed, such as modifying IL-12, utilizing viral vectors, non-viral vectors and cellular vectors. Previous studies have found that IL-12 fusion with extracellular matrix proteins, collagen and immune factors is a way to enhance its therapeutic potential. In addition, studies have demonstrated that viral vectors are a good platform, and a variety of viruses such as oncolytic viruses, adenoviruses and poxviruses have been used to deliver IL-12, and testing has been conducted in various cancer models. Local expression of IL-12 in tumors based on viral delivery avoids systemic toxicity while inducing effective anti-tumor immunity and acting synergistically with other therapies without compromising safety. Also, lipid nanoparticles are currently considered to be the most mature drug delivery system. Moreover, cells are also considered to be drug carriers because they can effectively deliver therapeutic substances to tumors. In this article, we will systematically discuss the antitumor effects of IL-12 on its own or in combination with other therapies based on different delivery strategies.