Purpose: This study aims to examine the applicability of an extended version of the theory of planned behavior (TPB) in predicting pro-environmental behavior, specifically the purchase behavior (PB) of package-free bath products, among students in higher education institutions (HEIs). Design/methodology/approach: Using a non-experimental survey research design, this study empirically tested an extended TPB model through structural equation modeling. The dataset was obtained through a survey of undergraduate students in three HEIs in the Philippines. Findings: Environmental knowledge (EK) predicted attitudes toward purchasing package-free bath products. Attitudes, subjective norms and pro-environmental self-identity (PSI) predicted intention to purchase package-free bath products. Furthermore, the intention to purchase package-free bath products and perceived behavioral control predicted PB of the said item. Research limitations/implications: The results imply that the addition of EK and PSI to the TPB is applicable in predicting pro-environmental behavior, specifically the purchase of package-free bath products. Practical implications: The results showed how HEIs can encourage their students to purchase package-free bath products. Social implications: The results highlight how social and economic factors play a role in promoting or inhibiting pro-environmental behavior among HEI students. Originality/value: The findings support the inclusion of EK and PSI to the TPB for an integrative model that aims to improve the prediction of the purchase of package-free bath products.