Resources such as education and social networks are likely to contribute to migrants' upward mobility in the class hierarchy. Moreover, according to structural fit theory, the contribution tends to be contingent on age and social network size. The contingency is the major concern of the present study of mainland Chinese migrants in Hong Kong, which is somewhat different from the Chinese mainland economically, politically and even culturally. In this study, we show that the conditions for upward mobility are some human and social resources and their various combinations. Notably, schooling after arrival in Hong Kong contributed more to the upward mobility of the migrant who was younger or had a larger social network at the time of arrival in Hong Kong. Purportedly, promoting the migrant's integration with the school and local social network would prepare the migrant for upward mobility.