The aim of this study was to evaluate the inclusion of molasses in garlic (Allium sativum) foliage silages and its effect on in vitro ruminal fermentation parameters and gases production including methane and CO₂. To this end, fermentation was carried out in 16 microsilos with the addition of molasses (T1 – garlic foliage 90%, ground maize 10%, molasses 0%; T2 – garlic foliage 85%, ground maize 10%, molasses 5%; T3 – garlic foliage 80%, ground maize 10%, molasses 10%; T4 – garlic foliage 75%, ground maize 10%, molasses 15%; n = 4) for 50 days. Subsequently, fermentation was carried out in microsilos using rumen fluid for nutritional evaluation. The inclusion of molasses affected protein, NDF, NSC and lactic acid contents, and pH (P < 0.05); protein and NDF decreased 22 and 12%, respectively, with the inclusion of 15% of molasses, and pH was generally reduced after the addition of molasses to the experimental treatments. However, molasses increased the NSC content and in vitro dry matter digestibility. Regarding ruminal fermentation, no changes were recorded in the proportions of volatile fatty acids (P > 0.05), while the concentration of total volatile fatty acids increased with the addition of molasses (P < 0.05). Ammonia-N levels decreased with the inclusion of molasses (P < 0.05), while maximum gas production increased up to 48%. Similarly, methane production increased by 46% at the maximum dose of molasses addition (P < 0.05), but no changes were recorded in the CH₄:CO₂ ratio (P > 0.05). These results suggested that the addition of molasses to garlic foliage silages did not result in significant changes in ruminal fermentation parameters such as volatile fat acid (VFA) levels. Therefore, garlic foliage silage can be applied without additional supplementation to reduce agricultural waste and as a nonconventional alternative in ruminant nutrition.