The main objective of this study was to evaluate the use of dairy manure compost (C) and vermicompost (V) as substrate components for organic production of lettuce seedlings in coconut coir. Eight substrates were tested: coconut coir (without fertilization), 3 binary mixtures of compost and coir (20, 40, and 60% by volume of compost: 20C; 40C and 60C), 3 binary mixtures of vermicompost and coir (20, 40, and 60% by volume of vermicompost: 20V; 40V and 60V) and a commercial substrate certified for organic farming (control). Lactuca sativa L. 'Lollo Rosso' seeds were sown in multi-cell plastic trays (17 cm3) filled with the 8 substrates and grown for 28 days. Increasing the percentage of compost and vermicompost on the mixture significantly increased the substrate electrical conductivity (EC, 1:6 by volume) from 17.6 mS m-1 (coir) up to 94.2 (60C) and 87.8 mS m-1 (60V), as a result of the high soluble salt content in dairy manure compost and vermicompost. However, EC values of 60C and 60V substrates exceeded the EC recommended values for seedlings. Compost and vermicompost did not affect lettuce seedlings germination but significantly enhanced seedling growth, namely dry and fresh weight, and number of leaves, when compared with coir substrate. No significant differences were found between growth of seedlings from control and seedlings from mixtures 20C and 20V. Moreover, seedling growth on the mixtures 40C, 40V, 60C and 60V was higher than on control substrate. Therefore, the materials tested in this study can be successfully used, in the convenient ratios, as substrate components for organic production of lettuce seedlings in coconut coir substrate.