In this study, we evaluated the influence of sour yogurt as a natural microbial inoculant in second-crop corn silages. For this purpose, two trials with different dilution rates were conducted. In Trial I, the groups 10 g sour yogurt + 5 g distilled water (SY10-2), 20 g sour yogurt + 10 g distilled water (SY20-2), 30 g sour yogurt + 15 g distilled water (SY30-2), 40 g sour yogurt + 20 g distilled water (SY40-2), 50 g sour yogurt + 25 g distilled water (SY50-2) and no additives were added to the control (CON) group. The groups in Trial II, 10 g sour yogurt + 10 g distilled water (SY10-1), 20 g sour yogurt + 20 g distilled water (SY20-1), 30 g sour yogurt + 30 g distilled water (SY30-1), 40 g sour yogurt + 40 g distilled water (SY40-1), 50 g sour yogurt + 50 g distilled water (SY50-1) and 10 g of distilled water were added to the control (WCON) group. For the silages opened on the 90th day of ensiling, the highest lactic acid content was determined in the SY20-2 and SY20-1 groups (p < 0.05). The lowest amount of ammonia nitrogen was in the SY30-2 group (p < 0.05). In the aerobic period, the SY10-2 and SY20-2 groups remained more stable than the others. As a result, the SY20-2, SY30-2, SY20-1, and SY30-1 groups improved the fermentation quality of corn silages, but the effect on aerobic stability was not significant and was similarly found with the homofermentative bacterial inoculants.