Objective  We investigated lifestyle changes and disease risk factors in Vietnamese workers after migrating to Japan.Methods  From January to March 2022, semi-structured interviews were conducted with 15 Vietnamese workers in Japan regarding their daily habits, focusing on diet and environmental changes. Data were analyzed qualitatively. Results  Six men and nine women (average age: 25.5 years) participated. Their residence status included Technical Intern Training (nine individuals), Designated Activities (two), and Engineer/Specialist in Humanities/International Services (four). Their periods of stay ranged from six months to eight years. We extracted 31 main categories (and 100 subcategories) from the interviews that indicated lifestyle changes from Vietnam to Japan. These changes included switching to an imbalanced diet, less fruit intake, greater snack intake, lower alcohol intake, and decreased physical activity after moving to Japan. Participants cited busy schedules (and therefore less time) as the primary reason for dietary changes and reduced physical activity in Japan. Additionally, stress levels rose significantly after migration, with some participants attributing that increase to lifestyle changes. Furthermore, despite reporting no major illnesses in Vietnam, health checkups after living in Japan identified disease risk factors, such as weight changes and negative health conditions (e.g., dyslipidemia, hypertension, liver dysfunction, and anemia). Conclusions  Our findings suggest that lifestyle changes are related to post-migration abnormalities in health screening outcomes, including weight gain and dyslipidemia. Recognizing and providing early support for these changes are important in preventing the onset or worsening of noncommunicable diseases among migrant workers.