Sugarcane (Saccharum officinarum) is an interesting feed source for cattle in tropical area, since the harvesting phase matches with the drought season which is a period of shortage of feed. The aim of this study was to determine the effects of commercial inoculant and chemical additives association on microbiological quality of sugarcane silage. Treatments were distributed to forty-eight mini-silos in a 2 × 4 treatment factorial arrangement composed by two levels of microbial inoculant (INO, 0 or 4 g t^-1 of fresh sugarcane; INO had Lactobacillus plantarum at 3.0 × 10¹⁰ cfu g^-1 and Propionibacterium acidipropionici at 3.0 × 10¹⁰ cfu g^-1), three chemical additives (CHE, CaO, NaCl and urea at 1.0% on natural matter basis), and a treatment without additives. Samples (0.2 kg) were collected on day 60 from different sites of all silos and homogenized to form a composite sample. Subsamples of 10 g of each treatment were diluted in 90 mL of sterilized sodium chloride solution (0.9%) and a serial dilution was performed from 10^-1 until 10^-6 in test tubes. The microorganism counting was performed in triplicate from each dilution using culture medium of MRS agar to lactic-acid bacteria, PCA (Plate Count Agar) to aerobic and anaerobic bacteria (48 h of incubation at 37ºC) and agar PDA (potato dextrose agar, 120h of incubation at 26ºC) for mold and yeast. Data were submitted to analysis of variance using the PROC MIXED by SAS version 9.0. Inoculants provided with CHE increased the amounts of lactic acid bacteria, anaerobic bacteria and total bacteria in sugarcane silage. In addition, the INO association with CHE decreased the fungi proliferation in the silage. INO increased the lactic acid bacteria in the current experiment. The association of INO and CHE or just the INO treatment had lower amounts of fungi, compared to treatments without CHE and INO or those treatments with CHE. L. plantarum isolated from grass silage produced antifungal compounds (3-phenyllactic acid and 3-hydroxydecanoic acid) in MRS. The association of INO and CHE positively affected the microbiological quality of sugarcane silage.