The objective of the research conducted was to optimize the fermentation conditions of pork sirloins and to assess the impact thereof on the sensory quality of dry-aged raw meat products with the addition of probiotic bacteria. The research material consisted of dry-aged pork sirloins and a probiotic strain of Lactobacillus casei LOCK 0900 (Patent Claim No.: P-382760). Two sirloin variants were studied: a control sample with the glucose added and a sample with the probiotic strain and glucose added. The samples of those two variants were aged in three temperature ranges (16, 20, and 24 °C). During the 21-day aging period, the aging meat samples were taken every 7 days in order to analyze them microbiologically. A sensory analysis was performed upon the completion of the aging process of the product. The number of lactic acid bacteria (LAB) was determined using a Tempo ® (bioMérieux, France) apparatus, which counted the number of micro-organisms, whereas the sensory evaluation was carried out by a Quantitative Descriptive Analysis (QDA) method. The highest LAB growth of bacteria, including the Lb. casei ŁOCK 0900 probiotic strain, was found in the pork sirloins during the 21-day aging period at 20 °C (from 10⁷ to 10⁸ log CFU/g). A high number of LAB was also found in the meat samples that aged at 24 °C (from 10⁶ to 10⁷ log CFU/g). The lowest growth of LAB, including the probiotic strain, was determined in the sirloin samples that aged at 16 °C (from 10⁴ to 10⁶ log CFU / g). The product samples that aged at 16 and 20 °C were characterized by the highest overall quality. As regards the microbiological and sensory quality, the optimal fermentation conditions of the dry aged raw sirloins with probiotic bacteria added are: aging temperature of 20°C and aging time of 21 days.