Purpose The purpose of this study is to explain the factors that affect the green buying behaviours and the relations between these factors. For this purpose, three main factors were added to the Ajzen’s theory of planned behaviour (TPB) to develop a more comprehensive model, namely, environmental concern, environmental knowledge and perceived consumer effectiveness (PCE). It is believed that these variables could help understanding the green buying behaviour and extending the TPB model. Design/methodology/approach In this study, quantitative research has been made to test the relations in the proposed model. The target population in this research is individuals living in Turkey, both sexes of age over 18 years. The data were collected through an online survey between May and August of 2017. The data were statistically analysed with structural equation modelling and interpreted using the statistical software AMOS version 20.0. Findings The findings show that PCE is the variable that has the highest influence on the attitudes towards behaviour, intentions and green buying behaviour in the proposed model. It is possible to say that the PCE variable added to the model is an important variable that improved and strengthened the measurement model. Variables added to the model are compatible with Ajzen’s original model. Research limitations/implications The obtained data may not be generalised throughout Turkey. However, it is believed that the data obtained can give a general idea for green buying behaviour of individuals in Turkey. Practical implications The obtained data provide a contribution to the marketing communication experts and the literature. Research findings contribute to explaining green consumption behaviours in developing countries. Originality/value In this research, the gap between consumers’ attitudes and their behaviours has been researched. Understanding the reason for this gap is essential to increase green consumption in developing countries. The number of studies in this field in Turkey is not very much. For this reason, this study is thought to contribute to the field.