In learning environments research, limited attention has been paid to the effects of the family environment on student thinking. This study constructed a five-dimension survey of the family environment, based on previous studies of the classroom learning environment, and used it to compare the effects of the family environment and the classroom learning environment associated with an interdisciplinary course (i.e., Liberal Studies) on the critical thinking disposition of 2189 secondary students in Hong Kong. Stepwise regression revealed that: the overall effects of the classroom learning environment of Liberal Studies on critical thinking disposition were greater than those of the family environment; the content-oriented dimensions of both environments were stronger predictors of critical thinking disposition than the relationship-oriented dimensions of both environments; and the effect of the dimension of challenging task on critical thinking disposition was stronger than that of other pedagogy-oriented dimensions. Also the means of all dimensions of the family environment were significantly lower than those of the corresponding dimensions of the classroom learning environment. It is suggested that more effort should be made to enhance both classroom learning environment and family environment to generate convergent forces to efficiently cultivate students' critical thinking.