Climate change poses significant risks to food security and contributes to widespread soil degradation. Effective strategies are urgently needed to mitigate its impacts and ensure stable crop production and food quality. Biochar has shown strong potential to reduce greenhouse gas emissions, enhance carbon sequestration, and immobilize soil contaminants such as heavy metals and organic pollutants. These benefits can lead to increased crop yields, improved nutritional quality, and reduced uptake of harmful substances by plants. This review summarizes the possible mechanisms through which biochar influences the biochar–soil–plant interface, aiming to provide a comprehensive understanding of its multifaceted roles. Although positive effects of biochar on crop production are frequently reported, neutral or even negative outcomes have also been observed. Such adverse effects may be attributed to the presence of volatile organic compounds, free radicals, or heavy metals in certain biochars that inhibit plant growth. Additionally, biochar application has been found to reduce plant infections caused by pathogens, likely due to the presence of organic compounds that act as microbial inhibitors. A deeper understanding of the mechanisms by which biochar affects plant growth is essential for its effective use as a tool to combat climate change and enhance food security.