There are very few publications reporting results of studies on effects of biologicals on yields and quality of bulbaceous plants. In view of this, our purpose was to scientifically substantiate effects of biologicals containing bacterial strains of Pseudomonas aureofaciens B-111 (IBM B-7096) and Pseudomonas aureofaciens B-306 (IBM B-7097) as well as spores and mycelium of the fungus Trichoderma viride on the yield and quality of shallot bulbs. To achieve the purpose, we set the following objectives: to investigate biometric parameters of shallot plants depending on biological treatments, to determine the yield and to evaluate the impact of the biologicals on the biochemical composition of bulbs. The biologicals increased in the mean bulb weight by 6–15% and the plant height by 9–15%. The total yield was raised by up to 16.2%. The share of marketable yield was increased by 1.2–7.0%. There was a slight increase in the ascorbic acid content in bulbs (by 3–22%) and a slight decrease in the dry matter content (0.24–1.35%). We also observed a slight decrease in the total sugar content (by 0.16–1.76%, depending on biologicals and shallot cultivars).