<p>The objective of the study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs) on the growth and nutrient absorption by tomato plants (<i>Solanum lycopersicum</i> L.), as well as the content of nutrients and biocompounds in tomato fruits, including primary and secondary metabolites, and soil quality indicators. The experiment was conducted in a greenhouse, using soil as a substrate. Treatments consisted of foliar applications or incorporation into the soil of MWCNTs suspensions at concentrations of 0, 100, 200, 400, or 800 mg L^− 1. The study was carried out until the fruiting stage (130 days after transplantation). The analyses of nutrients and metabolites in plants and fruits, as well as soil quality indicators, were determined and quantified using chromatographic and spectrophotometric techniques. As a result, foliar application (MW-F1) increased the microbial biomass of the soil; however, adding MWCNTs to the soil significantly reduced the microbial biomass. Direct soil application of MW-S1 increased the fresh and dry weight of the plants. It improved the content of total phenols, gallic acid, trans-ferulic acid, and trans-sinapic acid in tomato fruits. MW-S2 improved the dry weight of plants, the number of fruits per plant, and the absorption of cations in plants and fruits. Additionally, the treatment increased the content of malic acid, antioxidant capacity, carotenoids, and myricetin in tomato fruits. MW-S3 increased the content of proline, glutamic acid, antioxidant capacity, lycopene, malic acid, trans-ferulic and trans-sinapic acids, myricetin, potassium, and magnesium content in tomato fruits. MW-S4 treatment reduced gallic acid and increased chlorogenic acid in fruits. However, regardless of the type of application, MWCNTs reduced the protein amino acid content in tomato fruits. The direct addition of MWCNTs to soil was more effective in enhancing plant growth and metabolite production. However, such applications may compromise soil quality. Regardless of the type of application, MWCNTs, at specific concentrations, have the potential to act as elicitors in tomato, promoting the accumulation of bioactive compounds in the fruit. However, their use could reduce amino acid content, possibly as a metabolic response to induced stress. The direct application of MWCNTs to the soil proved to be more effective as an elicitor strategy; however, this method could compromise specific soil quality indicators, suggesting the need to assess its long-term sustainability.</p>