This research examined motivational trajectories during early adolescence in the United States and China. Upon their entry into middle school at 7th grade and every 6 months thereafter until the end of 8th grade, 825 American and Chinese children (mean age = 12.73 years) reported on their motivational beliefs (e.g., mastery orientation) and behavior (e.g., self-regulated learning strategies). The quality of children's motivational beliefs deteriorated over the 7th and 8th grades (e.g., children became less mastery oriented) in both the United States and China. American children also valued academics less, with declines in their motivational behavior as well. Chinese children continued to value academics, sustaining their motivational behavior. In both countries, children's motivational beliefs and behavior predicted their grades over time.