Mycorrhizal fungi increase plant resistance to stress factors such as drought, high or low temperatures, acidification, soil contamination with heavy metals, and the presence of soil pathogens. The aim of the study was to determine the effect of mycorrhizal inoculum on plant growth and the microbiome of the rhizosphere soil of tomato. The experiment was established in the greenhouse of the Felin Experimental Farm at the University of Life Sciences in Lublin. The research material consisted of tomato plants (Solanum lycopersicum L.) Lubań cv. The mycorrhizal inoculum Endo-VAM from Mykoflor (Końskowola, Poland) was used for mycorrhization of tomato seedlings. It contains spores and live mycelium of the following species: Glomus intraradices, G. mosseae, G. claroideum, G. etunicatum, Gigaspora margerita, and Entrophospora spp. Non-mycorrhized tomato seedlings served as a control. Six weeks after the application of the mycorrhizal inoculum, mycological analysis of tomato roots and microbiological analysis of rhizosphere soil were performed, and plant height, stem base diameter, fresh and dry root weight were determined. The roots of mycorrhized plants were found to be more abundantly colonized by fungi, including antagonistic species, than the roots of non-mycorrhized plants. The total number of bacteria, including Pseudomonas and Bacillus genera, and the total number of fungi isolated from the rhizosphere of mycorrhized plants were significantly lower than in the rhizosphere of control plants. Analysis of morphological parameters of tomato plants demonstrated a beneficial effect of the mycorrhizal inoculum on the growth of fresh and dry root weight, but did not demonstrate a significant effect of mycorrhiza on plant height or tomato stem base diameter.