This study’s objective was to examine direct and indirect relationships among family socioeconomic status, subjective social status, and achievement motivation within the first 3 months after college freshmen enrollment in China. A longitudinal dataset was collected over a 3-month period at four measurement points with 4-week intervals. A cluster sample of 1,983 college freshmen from the eastern, central, and western economic regions of China was surveyed. Latent growth modeling was conducted. The results indicated that achievement motivation decreased over time and was positively related to a decline in subjective social status. Mediation analyses demonstrated that, after controlling for sex and economic region, family socioeconomic status predicted the initial level of achievement motivation directly and indirectly through the initial level of subjective social status, and notably, the directions of these effects were opposite. Further, family socioeconomic status also significantly predicted the rate of change in achievement motivation indirectly through the initial level of subjective social status. These results highlight the longitudinal relationship between family socioeconomic status and achievement motivation via different pathways and have implications for improving college freshmen’s achievement motivation.