This article presented the diagnosis and treatment of three patients from the first imported familial clustering of clonorchiasis in Shanghai Municipality, and evaluated the value of different stool examination methods in non-endemic areas of clonorchiasis. In February 2026, the first case of clonorchiasis in this family was confirmed, and subsequent epidemiological surveys revealed that four family members all had a history of traveling to Guangdong Province and consuming raw freshwater fish. Stool samples were collected from all four individuals and detected for Clonorchis sinensis eggs using both machine smear method and the modified Kato-Katz thick smear method. C. sinensis infection was detected among three individuals using the Kato-Katz method, with severe [20 448 eggs per gram (EPG)], moderate (2 376 EPG), and mild infections (960 EPG) identified, respectively, and no C. sinensis eggs were identified in the remaining one stool sample. In contrast, only one infection was detected with the machine smear method, resulting in a underdiagnosis rate of 66.67% (2/3). All three confirmed cases were cured following standardized therapy. This article indicates that imported familial clustering clonorchiasis cases are highly occult in non-endemic areas, and the machine smear method has a high risk of underdiagnosis during initial screening. A two-tier diagnostic model combining “machine smear method for initial screening + Kato-Katz method for confirmation” is recommended.