Purpose This study aims to examine millennial consumers’ intentions towards purchasing eco-friendly products in the emerging Arab nation of Oman, focusing on the moderating role of eco-labelling (EL). Design/methodology/approach Environmental knowledge (EK) and environmental concern (EC) are integrated into the theory of planned behaviour (TPB) framework as independent variables, along with EL as a moderating variable. The data was collected through a self-administered survey and consisted of 705 random responses that was tabulated and analysed through the structural equation modelling technique. Findings ECs, subjective norms (SNs) and perceived behavioural control (PBC) significantly influence consumer attitudes towards green eco-friendly products. Consumers’ EK and attitudes positively influence the purchase intention (PI) to make green purchases. SNs and PBC substantially influence consumer attitudes towards adopting green products. However, the findings reveal a non-significant moderating influence of EL on the relationship between EC and PI for millennial Omani consumers. Research limitations/implications The findings are limited to only one Arab country, Oman, which limits the scope of the study. This study contributes to the TPB by using additional dimensions to examine the green purchasing behaviour of millennials. Practical implications Marketers can use these insights to develop strategies that emphasise the environmental benefits of products, leverage social influences and empower consumers to make environmentally conscious choices. Incorporating EL and green packaging can enhance the visibility and attractiveness of green products. Social implications Promoting environmental education, awareness campaigns and policy interventions that highlight the importance of eco-friendly product choices can foster more sustainable consumption patterns among Arab consumers. Originality/value To the best of the authors’ knowledge, this is the first study to examine the green PIs of millennials in an Arab context, specifically focusing on the moderating role of EL.