Opuntia stricta var. dillenii extracts exhibit anti-oxidative and anti-inflammatory properties, which are of significant interest for the prevention and management of metabolic dysfunction-associated fatty liver disease (MAFLD). The present study is the first to investigate the potential anti-steatotic effect of Opuntia stricta var. dillenii extracts. The aim is to evaluate the anti-steatotic effect of extracts from various parts of the plant (whole fruit, peel, pulp, and the industrial by-product, bagasse) in an in vitro model using both murine AML12 and human HepG2 hepatocytes. Results have demonstrated that all tested extracts, including those from the whole fruit, peel, pulp, and bagasse, exert an anti-steatotic effect. In murine hepatocytes, the whole fruit extract at 100 μg/mL and the peel extract at 10 μg/mL presented the highest capacity to reduce PA-induced triglyceride accumulation. In fact, the peel was the most potent extract, preventing lipid accumulation at the lowest dose used. In human HepG2 hepatocytes, the peel, pulp, and bagasse extracts at 100 μg/mL demonstrated the greatest triglyceride reduction, suggesting that the human model is less responsive. Regarding the main mechanism of action, the peel and pulp extracts seem to inhibit de novo lipogenesis. Additionally, the downregulation of the fatty acid transporter CD36 appears to contribute to the prevention of triglyceride accumulation in both extracts.