<p>African American adolescents are at risk of living in obesogenic environments, which may contribute to low-quality dietary intake and associated obesity risk. Family mealtime builds capacity for health behaviors; however, limited studies have assessed facilitators or barriers of family mealtime using an ecological approach among African American families. This study longitudinally (baseline, 8 weeks, 16 weeks) evaluated a range of ecological factors as predictors of family mealtime frequency and quality among 151 overweight African American adolescent-parent dyads (adolescent <i>M</i>age = 12.9 ± 1.7; <i>M</i>BMI%=96.3 ± 4.4; %female = 60.9% [adolescent], 96.0% [parent]) that participated in the Families Improving Together (FIT) for Weight Loss trial. Multilevel model analyses demonstrated a significant two-way interaction between perceived neighborhood healthy food access and time (<i>B</i> = 0.11, <i>SE</i> = 0.05, <i>p</i> = 0.025), such that greater perception of neighborhood access to healthy foods was associated with increased family mealtime quality over time. Further, a significant two-way interaction between family social support for healthy eating and time (<i>B</i> = 0.13, <i>SE</i> = 0.06, <i>p</i> = 0.018), such that higher levels of reported social support were associated with increased family mealtime quality over time. Finally, a marginal two-way interaction between parental limit-setting on health behaviors and time (<i>B</i> = 0.19, <i>SE</i> = 0.10, <i>p</i> = 0.069), such that greater limit-setting was associated with increased family mealtime frequency over time. These findings indicate the importance of environmental and interpersonal support in supporting family mealtime frequency and quality in African American families.</p><p> <?noindent??><b>Trial registration</b> ClinicalTrials.gov # NCT01796067. The trial was registered on February 21, 2013, and the first participant was enrolled July 12, 2013.</p>