Tropical highland blackberry by‐product (BBP) has high amounts of polyphenols including ellagitannins (ET) and anthocyanins (ATC). Information of the effect of different operations on ET is scarce. In this study, pseudo‐first and first order kinetic models and response surface methodology were applied to optimize the extraction of polyphenols from BBP using ethanol, a food grade solvent. Retention of total polyphenols, ET and ATC was analyzed considering their contents before and after the application of thermal vacuum concentration, ultrafiltration, and spray drying. The optimal conditions for extraction were: a 3.4 solvent/BBP ratio, 57.1% ethanol, 60.0°C, and 120 min extraction time. Thermal vacuum concentration showed a higher retention of ET. A higher purity of ET was accomplished with ultrafiltration. These results provide the basis for further research on the development of a powder enriched with polyphenols, mainly ET, from BBP for food and pharmacological purposes. Practical applications Ellagitannins (ET) are a group of polyphenols found in tropical highland blackberries grown in Costa Rica, mainly in their seeds that are discarded as a by‐product (BBP) during blackberry processing. The production process of an ingredient with high amounts of ET has not been widely reported. In this study, modeling and optimization of an ethanolic extraction of polyphenols from BBP, and the effects of thermal vacuum concentration, ultrafiltration and spray drying on polyphenolic compounds were analyzed. This information will lead to further experiments on the effective recovery of ET in order to produce a nutraceutical product, which is not only complementary to the diet, but may also aid in the prevention and treatment of diseases, or an ingredient to be used in the production of functional foods.