A composted material obtained from forestry wastes and solid phase of pig slurry was evaluated as a substrate component for the production of tomato and lettuce seedlings. Four different substrates were tested: compost (100C), a mixture of 75% compost and 25% peat substrate (75C), a mixture of 50% compost and 50% peat substrate (50C), and peat-based substrate (control). Compost increased the pH of the substrate from 6.3 (control) to 6.9 (100C) but did not affect the electrical conductivity (0.26 and 0.27 mScm(-1), respectively, for control and 100C). Germination and growth of lettuce seedlings were not affected by the substrate type, contrasting with tomato seedlings where the highest growth occurred at 100C substrate. Increasing compost percentage on substrate increased nitrogen, calcium and magnesium availability and, consequently, the concentration of these elements in plant tissues increased. On the contrary, potassium and manganese concentration decreased. Results from the study suggest that the compost studied is a good alternative to peat-based substrates for the production of vegetable seedlings.