This study aimed to characterize the in vitro effect of different products on the mycelial growth and conidial germination of Alternaria tomatophila, the etiologic agent of tomato early blight. The experiment was installed using a completely randomized design, in factorial scheme 5x4, with five levels of concentration (0%, 25%, 50%, 75% and 100% of the commercial recommended doses) x 4 products (cymoxanil + mancozeb, copper oxychloride, potassium phosphite 0-28-26 and biofertilizer) in four replicates. The products were added and homogenized to the PDA mean, to evaluate the inhibition of mycelial growth and incorporated in agar-water mean to test inhibition of conidial germination. The fungicide cymoxanil + mancozeb and the potassium phosphite 0-28-26 were the best evaluated products totally inhibiting the mycelial growth; the copper oxychloride was shown to be intermediary while the biofertilizer was less effective. The products behaved in a similar way in the conidial germination. The fungicide cymoxanil + mancozeb and the phosphite stood out, followed by copper oxychloride and the biofertilizer, however, the products did not completely inhibited the conidial germination of A. tomatophila.