Parents play a significant role in adolescent health behaviors; however, few nutrition interventions for Hispanic adolescents involve parents. This study assessed the effects of a 10-week parenting intervention simultaneously targeting nutrition and substance use prevention. Hispanic parent/6th–8th-grade adolescent dyads (n = 239) were randomized to Families Preparing the New Generation Plus (FPNG+; nutrition/substance use prevention), FPNG (substance use prevention only), or Realizing the American Dream (RAD; academic success control). Surveys assessed diet, alcohol use, substance use intentions, and substance use norms at baseline (T1), immediately post-intervention (T2), and at 16 weeks post-intervention (T3). Latent change modeling assessed diet changes; adolescent substance use outcomes were assessed using effect sizes. Among adolescents, those in FPNG+ increased fruit (+0.32 cup equivalents, p = 0.022) and fiber intake (+1.06 g, p = 0.048) and did not change added sugars intake at T2; those in FPNG and RAD reduced their intake of fruit and fiber (p < 0.05 for both). FPNG+ parents marginally increased fruit/vegetable intake (+0.17 cup equivalents, p = 0.054) and increased whole grains intake (+0.25-ounce equivalents, p < 0.05), in contrast to the reduction among RAD and FPNG parents (p < 0.05). Reductions in added sugar intake at T2 were greater among FPNG and FPNG+ parents relative to RAD parents (p < 0.05). FPNG+ and FPNG had comparable substance use outcomes (i.e., both had lower alcohol use and intentions to use substances relative to RAD). Engaging parents in a nutrition and substance use prevention parenting intervention yielded positive changes in dietary intake and maintained substance use prevention outcomes among their adolescent children.