Warm-season annual legumes can be used for forage, but there is little information about their use as silage. The objective of this study was to assess fermentation of four annual legumes when treated with or without a microbial inoculant specific for alfalfa (Pioneer 11H50). Two lablabs [Lablab purpureus (L.) Sweet] cv ‘Rio Verde’ (RVS) and ‘Rongai’(ROS), cowpea (Vigna unguiculata L. Walp.) cv ‘Iron and Clay’ (CPS), and sunn hemp (Crotalaria juncea L.) cv ‘Tropical sunn’ (SHS) were sown on 6 June , 2010, and harvested 76 days later (22 August). Maturity at harvest among legumes ranged from vegetative to 10% green pods. Legumes and fourth harvest alfalfa (AS) were cut same day and wilted for 18 h. Legumes were chopped to a particle size of 30 mm. A 500-g subsample was placed in a plastic bag either with or without inoculant, vacuum sealed and fermented for 150 d at room temperature (20^oC). Ensiled legumes were analyzed for nutritive value and fermentation characteristics as a 2 x 5 factorial experiment with three replicates. Inoculant by legume interaction was significant (P < 0.05) for in vitro true digestibility (IVTD), neutral detergent fiber digestibility (NDFD), pH, and organic acids composition. Except for AS, IVTD and NDFD were lower (P < 0.05) in the inoculated legumes than non-inoculated. The inoculant decreased pH (P < 0.05) below 4.7 in all legumes, except in CPS (4.86). Lactic and acetic acid concentrations were contrasting among legumes. The inoculant increased lactic acid (P < 0.05) in RVS and SHS, while decreased in CPS, AS, and ROS. Also, the inoculant increased (P < 0.05) acetic acid of CPS and SHS without affecting other legumes. Even though the inoculant was specific for AS, fermentation was different in all four annual legumes either by deceasing pH or modifying organic acid concentrations.