Non-communicable chronic diseases are associated with a low-quality diet, low physical activity, and sedentary behavior. To assess how parents' diet and physical activity habits were associated with their offsprings' lifestyles. A cross-sectional analysis of 8-16-year-old children and adolescents (n = 2539; 51.9% girls) was carried out within the frame of the first edition of the Physical Activity, Sedentarism, Lifestyles, and Obesity in Spanish Youth study (PASOS-2019). Data on adherence to the Mediterranean Diet (MedDiet), daily moderate-vigorous physical activity (MVPA), and screen time per day (television, computer, video games, and mobile phone) were collected from children and adolescents, and data on parents' diet quality and physical activity were compiled. Logistic regression models were used to assess the association between parents' lifestyles and those of children and adolescents. High diet quality of parents was associated with higher adherence to the MedDiet of children and adolescents, as well as high consumption of fruit, vegetables, fish, nuts, and legumes. The high physical activity level of parents was associated with the low consumption of fast foods, sweets, and candies in children and adolescents. Children with high levels of physical activity were those whose parents showed better diet quality and physical activity levels. Parents' high diet quality and physical activity were associated with healthy lifestyles, higher adherence to the MedDiet, and physical activity of their offspring, mainly in adolescents.