The present study aimed to identify the factors that prohibit or enable breast cancer survivors from adopting a healthy lifestyle, as well as to record patients’ suggestions towards developing a weight-loss lifestyle intervention. Twenty-three breast cancer survivors participated in four online, semi-structured focus groups in Greece. All discussions were video-recorded and transcribed verbatim. Participants were 50⋅5 ± 7⋅4 years old with a current mean BMI of 29⋅1 ± 3⋅4 kg/m2. Four main themes emerged from thematic analysis: (1) dietary and lifestyle practices, (2) the effects of cancer on body weight, (3) the impact of cancer on psychology, and (4) the effect of the environment on body weight. Lack of information from healthcare professionals and lack of time were the main barriers to body weight management, whereas the main facilitators were support from their social environment, along with a comfortable physical environment, and the facility of technology. Participants suggested that an effective weight-loss lifestyle intervention should include psychological and social support, guidance and education, collaboration, flexible recommendations, personalised goals, and a follow-up plan. The needs of breast cancer survivors need to be considered when designing weight-loss lifestyle interventions. A personalised approach may prove more effective in promoting a healthy lifestyle and improving patients’ care.