The use of organomineral fertilizers (OF) in the cultivation of vegetables has been considered a promising technology to provide nutrients gradually. The OFs can reduce the phosphorous (P) soil adsorption and leaching of nitrogen and potassium with the supply of some micronutrients. This study aimed to evaluate doses of OF as a source of P and micronutrients (boron and zinc) for curly lettuce cultivation. Five OF doses were evaluated: T1 = 0% (no P2O5 fertilization); T2 = 50% (75 mg/dm3 of P2O5); T3 = 100% (150 mg/dm3 of P2O5); T4 = 150% (225 mg/dm3 of P2O5); T5 = 200% (300 mg/dm3 of P2O5) of the lettuce recommended fertilization; T6 = 100% mineral fertilizer (MF) (150 mg/dm3 of P2O5). The fresh (FM) and dry mass (DM) of the lettuce shoot (aerial part), the soil nutrient level, and the plant nutritional status at harvest were evaluated. We observed that (i) the doses of 225 and 300 mg/dm3 of P2O5 via OF provided the same availability of P in the soil as the dose of 150 mg/dm3 of P2O5 of MF; (ii) the doses of 225 and 300 mg/dm3 of P2O5 of OF provided higher levels of soil boron and zinc compared to other treatments and (iii) the MF fertilization was more efficient than that of OF in the production of curly lettuce in a protected environment.