Online appearance preoccupation is a known correlate of poorer body image, social problems, and mental health symptoms among youth. Yet, this study is the first to investigate individual and social risks and resources expected to explain the level of concurrent, as well as change in, online appearance preoccupation across one year. We focused on two risk factors of appearance teasing online by peers and appearance-based sensitivity to rejection, and two positive resources of appearance neutral support from important others and ways of coping with appearance-related stressors. A total of 752 Australian adolescents and emerging adults (14–21 years; M = 17.8 years, SD = 1.8 years; 41% young men; about 95% White or Asian) recruited from secondary schools or university were included. Results of regression analyses suggested that, concurrently, online appearance teasing, appearance rejection sensitivity, and positive coping were uniquely associated with online appearance preoccupation. Further, the positive association of peer appearance teasing with online appearance preoccupation was stronger among young men than young women. Over time and once all risks and resources were considered, positive coping with appearance pressures was associated with a decrease in online appearance preoccupation from T1 to T2. Gender (girl/young woman) and intensity of social media use were notable risks for concurrent online appearance preoccupation and predictors of increases in preoccupation over one year. Findings are discussed in light of theory and provide practical suggestions for future research and interventions among youth.