Objectives: This study aimed to assess the impact of an educational intervention on middle-aged women's knowledge and behaviour regarding various aspects of a healthy lifestyle. Design: Quasi-experimental study involving 150 middle-aged women (divided into experimental and control groups). Setting: Participants were selected from health centres of Tehran, Iran. Method: Data collection included demographic information, knowledge of a healthy lifestyle and healthy lifestyle behaviour. Participants in both the intervention and control groups completed the questionnaires before and 2 months after the educational intervention. The intervention involved 10 minutes of face-to-face training followed by distribution of training booklets provided by the Ministry of Health in Iran. Statistical analyses were conducted using SPSS. Results: Within the intervention group, significant differences were observed in total healthy lifestyle knowledge and subscales for physical activity knowledge, anthropometry knowledge, healthy diet knowledge, and smoking knowledge, between the pre- and post-intervention periods. Other than for smoking behaviour, there was no significant difference in healthy behaviours pre- and post-intervention for the experimental and also the control group. Conclusion: While there was an increase in knowledge about healthy lifestyles following the intervention, this knowledge increase was not associated with a change in healthy lifestyle behaviours. Attention should therefore be given to other influences including socio-economic factors, mental health status, environmental factors, cultural influences, duration of the intervention and psychological factors if changes in healthy behaviour are to be achieved