Microorganisms experience intra- and inter-species interactions in the soil, and how these interactions affect the production of microbial volatile organic compounds (VOCs) is still not well-known. Here we evaluated the production and activity of microbial VOCs as driven by bacterial intra-species community interactions. We set up bacterial communities of increasing biodiversity out of 1–4 strains each of the Gram-positive Bacillus and Gram-negative Pseudomonas genera. We evaluated the ability of each community to provide two VOC-mediated services, pathogen suppression and plant-growth promotion and then correlated these services to the production of VOCs by each community. The results showed that an increase in community richness from 1 to 4 strains of both genera increased VOC-mediated pathogen suppression and plant-growth promotion on agar medium and in the soil, which was positively correlated with the production of pathogen suppressing and plant growth-promoting VOCs. Pseudomonas strains maintained while Bacillus strains reduced community productivity with an increase in community richness and produced eight novel VOCs compared with the monocultures. These results revealed that intra-species interactions may vary between Gram-negative and Gram-positive species but improved VOC-mediated functioning with respect to pathogen suppression and plant-growth promotion by affecting the amount and diversity of produced VOCs potentially affecting plant disease outcomes.