Background: Surgery such as mastectomy is frequently used to treat breast cancer in women, which has an impact on their quality of life. Both the physical and psychological needs of the women having mastectomy should be met, and their families must be involved in this care. However, psychological treatment is frequently neglected, including the giving of competent guidance, emotional support, and knowledge. Aim: To determine the effect of social media-based instructional guidelines on emotional status and quality of life for women undergoing mastectomy.Design: Pre& post-test using a quasi-experimental study design was used. Settings: The study was carried out in Egypt at Sohag City. Sample: From Facebook and WhatsApp groups, a purposeful sample of all available (300) women who had undergone mastectomy was collected in 2023. The online Google form spreadsheet was open from February 4 until February 25-2023. Tools: (I): A self-administered questionnaire (pre and post-testformat) to assess post-mastectomy women's demographic characteristics and medical history; post-mastectomy women's knowledgeabout mastectomy (II): Depression, Anxiety, and Stress Scale (DASS); and (III):Quality of Life (QoL) scale. Results: showed that there was (85%) of women had an unsatisfactory level of knowledge pre-implementation compared to (90%) of them had a satisfactory level of knowledge post-implementation of social media-based instructional guidelines. Also were highly statistically significant variations in the knowledge of mastectomy among women and their levels of stress, anxiety, and depression before and after the adoption of the social media-based instructional guidelines. Additionally, after the social media-based educational guidelines were implemented, there were significant QoL increases (p<0.001). Conclusion: The study concluded that social media-based instructional guidelines implementation generated significant gains in the post-mastectomy women's knowledge has a good impact on reducing emotional disturbance such as depression, anxiety, and stress, and quality of life among women having a mastectomy. Recommendations: As a new teaching strategy for demonstrating health issues, the social media-based instructional guidelines should be carefully developed and implemented for all women having mastectomy.