Pereskia aculeata Mill., a species of the family Cactaceous, popularly known in Brazil as ora-pro-nobis, has high protein, vitamin and mineral contents. High essential amino acid concentrations should be underscored, suggesting a better evaluation of the fractions. Current study quantifies amino acid content and the chemical score (CS) of protein amino acids, determining in vivo digestibility, protein efficiency ratio (PER) and net protein ratio (NPR) of P. aculeata. Plant material was collected, washed, placed in an oven at 60 °C, ground and stored in a freezer for chemical analysis. Diets that maintain isoproteic and isocaloric characteristics were prepared for the bioassay, namely: casein (no protein) and Pereskia aculeata leaves-based flour. Eighteen male albino Wistar rats, divided into three experimental groups of 6 animals each, were used to evaluate protein quality and bioavailability of micronutrients. Pereskia aculeata flour provided as a single source is inadequate for growth, although it is relevant for maintaining protein metabolism indicated by net protein ratio (2.87). It is actually a good quality protein source due to few limiting essential amino acids, and it meets the diet requirements for humans.Keywords: Ora-pro-nobis; protein quality; digestibility; PER; NPR; PDCAAS.Practical Application: Pereskia aculeata when provided as a single source is not adequate for proper growth, however it is important the adequacy of maintaining the protein metabolism indicated by net protein ratio. During the experiment, animals fed on Pereskia aculeata gained less weight when compared with animals fed on casein, mean weekly feed consumption was also low. And it is a good protein source good quality due to present few limiting essential amino acids and thus are able to meet the needs for the diet in humans.