In this study, we examined the sociological characteristics, health fitness, and physical activity levels of 372 patients with lung cancer who received their first chemotherapy in a tertiary hospital in Wuxi, China, and analyzed their associations with quality of life (QoL). Standardized measures were used to assess body composition, muscular function, cardiorespiratory fitness, and flexibility. Physical activity was measured using the International Physical Activity Questionnaire, and QoL was evaluated using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Lung Cancer 43. Higher physical activity levels were positively correlated with global health status but also linked to greater symptom burden and reduced functional limitations. Muscle mass, grip strength, and 6-min walk distance were positively associated with global health and inversely associated with symptom severity and functional scales. Females tended to report higher symptom burdens and lower functional scores. Multivariate analysis indicated that sex, educational level, comorbidities of chronic diseases, disease stage, and activity levels were associated with QoL measures. These findings suggest that better overall health and physical fitness, along with higher levels of physical activity, may be associated with improved QoL among patients with lung cancer.