This study examined changes in subjective well-being (SWB) during early adolescence (seventh grade-ninth grade). We treated SWB as a latent variable, which was measured by life satisfaction, negative emotions, and positive emotions, and employed a growth curve model-to-model change. Aspects of family structure (e.g., parental marital status and members in the household) were included as time-varying covariates. Using a Taiwanese sample (N = 2,510), we found that SWB declined during early adolescence. Furthermore, we found that having an intact family with a discordant marriage was detrimental to SWB at each time point. Moreover, we also found that adolescents from an intact family with a good intra-parental relationship and where grandparents were co-resident experienced better SWB at the second and the last year, respectively, of junior-high school than did their counterparts who stayed in an intact family without cohabiting grandparents.