Introduction: Obesity is a chronic, relapsing, and progressive disease. The issue of obesity affects 50 to 80% of patients who have been diagnosed with breast cancer. The aim of this study is to assess the scale of the problem of obesity among breast cancer survivors (BCS) older than 60 years, evaluate their physical fitness, and study the relationship between the occurrence of obesity and levels of fitness among breast cancer survivors. The relationship between fitness and sociodemographic factors has also been analyzed. Materials and Methods: This original epidemiological clinical study included a cohort of 88 female breast cancer survivors treated in 2022 in Holycross Cancer Center, Kielce, Poland. A questionnaire involving demographic information and medical data was utilized. The Senior Fitness Test (SFT) battery has been used to assess the physical fitness of the patients. Body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were also analyzed. Results: More than 70% of the studied breast cancer survivors were classified as overweight or obese, according to BMI and WC indices. Depending on the SFT trial, the regression coefficients indicated worse results in participants who were older, lived in urban areas, were professionally active, less educated, and had higher obesity indices. The analysis of the relationship between obesity indices and fitness components revealed that all obesity indices were significantly associated with lower body flexibility (BMI p = 0.0118, WC p = 0.0092, WHR p = 0.0364, WHtR p = 0.0095). Upper body flexibility was significantly correlated with BMI indices (p = 0.0091, p = 0.0193) and WHtR (p = 0.0095). Agility and balance were significantly associated with WC (p = 0.0193), WHR (p = 0.098), and WHtR (p = 0.0095). Lower body strength was significantly correlated with the WHR index (p = 0.0487). Significant differences were found in upper body strength depending on the WHtR category. Conclusions: In the studied group of breast cancer survivors, there is a high prevalence of overweight and obesity. With increasing obesity rates, older age, and lower education levels, physical activity measured by the SFT decreases. Living in urban areas and being professionally active also predispose to lower physical activity levels. As obesity indices increase, physical fitness decreases in trials assessing upper and lower body strength, upper and lower body flexibility, as well as agility and dynamic balance.