Lung cancer is intricately associated with genetic susceptibility, leading to familial clustering among affected individuals. This cross-sectional study aimed to assess the knowledge, attitude, and practice (KAP) toward lung cancer risk among the offspring of lung cancer patients. This study was conducted at Guangdong Provincial People’s Hospital between April 2023 and August 2023. Participants’ demographic characteristics and KAP toward lung cancer risk were collected through questionnaires. A total of 481 valid questionnaires were enrolled, with 243 (50.52%) males, and 242 (50.31%) aged > 40 years old. The mean scores for knowledge, attitude, and practice were 8.54 ± 2.60 (range: 0–13), 25.93 ± 3.16 (range: 7–35), and 17.47 ± 4.30 (range: 5–25), respectively. Structural equation modeling indicated that knowledge exerted a negative direct effect on attitude (β = − 0.417, P = 0.006) but a positive direct effect on practice (β = 0.733, P = 0.025). Additionally, attitudes displayed a negative direct effect on practice (β = − 1.707, P = 0.002). In conclusion, offspring of lung cancer patients exhibited insufficient knowledge, positive attitude, and suboptimal practice toward lung cancer risk.