Alfalfa crop is largely used worldwide in ruminant nutrition. Preserving this crop via ensiling and obtaining a high-quality stable silage, especially after a short period of fermentation, could be difficult due to the high buffering capacity and low content of water-soluble carbohydrates. Silage inoculants can be used for enhancing fermentation and aerobic stability of silage when exposed to air during feed out. The objective of this study was to evaluate the effects of a silage inoculant on fermentation parameters and aerobic stability of alfalfa silage after very short periods of fermentation. Three mini-silos (20 l volume) for each treatment were filled with wilted alfalfa crop (181 ± 6.6 kg DM/m³, 50.5% DM). Control forage (C) was treated with no inoculant and experimental treatment was inoculated with SiloSolve FC (FC) containing 50:50 of Lactobacillus buchneri (DSM22501) and Lactococcus lactis (DSM11037). The target application rate was 150,000 cfu/g of forage. The wilted crop was analyzed for composition before ensiling (DM 50.5% as fed; CP 18.2%DM; pH 6.15; NDF 47.9%DM; ADF 36.7%DM). The mini-silos were stored for 2, 4, 8, 16, and 32 d at 20°C. After fermentation, each mini-silo followed an aerobic stability (AS) test for 15 d for each point of fermentation. The AS test was performed by aerobically challenging the mini-silos and monitoring the temperature increase inside the forage mass. The data were analyzed by SAS 9.3 with a completely randomized design and a factorial arrangement of treatments (main effects inoculum, ensiling time and their main interaction). Means were post-hoc compared by Tukey's test. The use of SiloSolve FC significantly enhanced the acetate levels at all ensiling time points (P < 0.05). Aerobic stability was increased on average by 4 d in FC inoculated alfalfa silages compared with C (P < 0.05) at all ensiling periods (P < 0.05) and was especially clear after 4 and 8 d of fermentation, where AS was increased by 6 d (P < 0.05) in the inoculated mini-silos. These results demonstrate that the use of SiloSolve FC improves aerobic stability and fermentation of a legume crop that is difficult to ensile even after a very short period of fermentation.