This study explores the relationships between environmental attitude, green product knowledge, attitude towards purchasing green products, green product purchasing intention, and green purchasing behaviour. Using a cross-sectional survey approach, a random sample of 284 undergraduate students in a Zimbabwean polytechnic completed a self-administered questionnaire. Structural equation modelling (maximum likelihood estimation) was used to analyse the data. The findings indicate that there are positive associations between the following pairs of variables: environmental attitude and attitude towards green purchasing; green product knowledge and green purchasing intention; green product knowledge and green purchasing behaviour; attitude towards green purchasing and green purchasing intention; green purchasing intention and green purchasing behaviour; as well as a non-significant relationship between green product knowledge and attitude towards green. The findings reported that the Theory of Reasoned Action fully supported the students’ intention to buy green products, which then affects their green purchase behaviour. The inclusion of additional constructs to the proposed model was partially supported. The study results highlight the importance of considering product knowledge and other attitudinal factors—specifically environmental attitude and attitude towards green purchasing—when marketing environmentally-friendly products to college-level students.