This study aimed to evaluate the effects of ground wheat grain, formic acid and a bacterial inoculant on fermentation quality, chemical composition and estimated feeding value of hemp silage. Industrial hemp (Cannabis sativa L.) was harvested at the full-flowering stage, chopped to 1–2 cm fragments and ensiled using four treatments: control (no additive), 5% ground wheat grain, 0.5 kg/t formic acid and 0.05 ml/kg bacterial inoculant, each prepared in triplicate. Fresh hemp showed high concentrations of neutral detergent fibre (79.46%), acid detergent fibre (65.48%) and acid detergent lignin (11.55%), together with low crude protein (3.41%) and water-soluble dry matter, indicating limited fermentability. Additives significantly influenced silage pH and Fleig scores (P < 0.001). Formic acid addition resulted in the most favourable fermentation profile, with the lowest pH (4.56) and highest Fleig score (92.64). Ground wheat increased water-soluble dry matter, Brix values, and crude protein content (4.88%) and improved silage quality. In contrast, bacterial inoculant caused only a minor decrease in pH, likely due to the low sugar content and high buffering capacity of hemp forage. Energy-related parameters, including total digestible nutrients, metabolizable energy and net energy fractions, were not significantly affected by additives, likely due to the fibrous and lignified structure of hemp. However, the improvement in relative feed value caused by wheat grain addition indicates that carbohydrate supplementation can partially improve feeding value of hemp silage. Overall, industrial hemp is a low-protein, high-fibre forage with limited fermentability, although formic acid and carbohydrate-based additives can improve its fermentation characteristics.