Opuntia stricta var. dillenii, a member of the Cactaceae family, produces a fruit known as prickly pear. This fruit is rich in bioactive compounds, including betalains and phenolic compounds, which play an important role in health promotion due to their antioxidant and anti-inflammatory properties. This study aims to investigate the impact of prickly pear extracts obtained from the whole fruit, peel, pulp, and an industrial by-product (bagasse) on the differentiation of 3T3-L1 pre-adipocytes. During the differentiation process, 3T3-L1 pre-adipocytes were treated with prickly pear extracts at concentrations ranging from 10 to 100 μg/mL from day 0 to day 8 post-induction. Moreover, the potential mechanisms justifying the observed effects were assessed by RT-PCR. All extracts led to an increase in both triacylglycerol accumulation and cell number. In conclusion, the analysed extracts demonstrated adipogenic effects in 3T3-L1 maturing pre-adipocytes by increasing the expression of the c/ebp-β, srebf-1, and c/ebp-α genes. Additionally, a potential anti-inflammatory effect was observed through the upregulation of adiponectin.