The use of pesticide in modern agriculture has raised concerns about impacts on non-target organisms, especially in the early stages of plant development, when sensitivity to chemical stressors tends to be higher. The commercial fungicide formulation, NATIVO®, which combines tebuconazole (triazole) and trifloxystrobin (strobilurin), represents an efficient agronomic strategy due to its different modes of action, but this combination may intensify adverse effects on the environment. This study investigated the phytotoxic potential of NATIVO formulation on Lactuca sativa and Triticum aestivum seeds, according to OECD 208 and ISO 18763 guidelines. Eight concentrations were evaluated, equivalent to 0.2–18.6 mg/L of tebuconazole (TEB) and 0.1–9.3 mg/L of trifloxystrobin (TRI), in addition to negative and positive controls. After incubation for 72h at 24°C in the dark, germination rate, germination speed index (GSI), and root and aerial growth were analyzed. The results showed greater sensitivity of L. sativa, with a significant reduction in GSI at higher concentrations and consistent inhibition of root and shoot growth at all concentrations tested, indicating compromised initial vigor. In T. aestivum, the response was less pronounced, although root growth was reduced at all concentrations, suggesting that the root system is one of the main targets of the formulation. The commercial formulation NATIVO® demonstrated significant phytotoxic potential, indicating that exposure to commercial mixtures may pose a real risk to the initial establishment of agricultural crops and non-target species. These findings reinforce that the effects observed are not restricted to the isolated active ingredients, but result from the interaction between components of the formulation, highlighting the need for ecotoxicological approaches that consider the commercial product as a whole for a more realistic environmental risk assessment.