More than 160 public policies have been introduced, globally, to reduce the consumption of plastic bags, with a specific focus on plastic carrier bags. In Europe, these policies have successfully influenced consumer behaviour, while in Africa, the impact remains uncertain due to policy failures or a lack of information. It is well-established that consumer behaviour, which includes psychological and social factors, plays a crucial role in reducing plastic consumption. This research specifically aimed to explore consumer behaviour related to the consumption of plastic carrier bags in Namibia, where people continue to purchase these bags even after the introduction of a plastic carrier bag levy. The study applied the Theory of Planned Behaviour (TPB) to understand consumer behaviour related to plastic carrier bags in Namibia, with a specific focus on Walvis Bay as a case study area. The TPB posits that the intention to perform a behaviour can be accurately predicted by one's attitude toward the behaviour, social norms, and perceived behavioural control. Intention, along with perceived behavioural control, predicts the actual behaviour of consumers regarding plastic carrier bag use. Self-reported data, collected through a TPB-based survey questionnaire, was administered at the household level. A total of 191 households from four suburbs in Walvis Bay (Kuisebmond, Narraville, Hermes and Meersig) participated in the research. Self-reported data were supplemented by observations of the proportions of plastic carrier bags in household plastic waste. Approximately 60.4% of respondents mistakenly believed that the prices of plastic carrier bags were uniform, despite variations. Situational factors, convenience, and environmental awareness were found to significantly influence plastic carrier bag purchasing behaviour. However, neutral scores in perceived behavioural control and social norms indicated a lack of clear social expectations and confidence when making decisions about plastic bag purchases. Furthermore, the study revealed that factors such as education, age, and income level significantly influenced the constructs within the TPB and the proportion of plastic bags in household waste. On average, households used between 7.8 and 11.3 plastic bags each week, with 47.3% of these bags being reused for waste disposal. This pattern of reusing plastic bags at home contributed to the continued purchase of such bags, suggesting that addressing the plastic bag levy should be approached from a solid waste management perspective. These findings provide valuable insights into the dynamics of plastic bag use and support the need for a comprehensive approach to address plastic waste management. Keywords: plastic carrier bag, plastic levy, waste management, Theory of Planned behaviour.