Background <p>Maternal depressive symptoms are a well-documented risk factor for adolescent depression, yet the symptom-level mechanisms of intergenerational transmission remain insufficiently understood.</p> Methods <p>A total of 1140 mother–adolescent dyads completed the PHQ-9 at baseline (T1), with 921 dyads reassessed 6 months later (T2). Cross-lagged panel network analysis was applied to examine symptom-level stability, cross-symptom predictions, and intergenerational associations across time.</p> Results <p>The analysis revealed strong autoregressive effects for maternal sleep disturbance and adolescent suicidal ideation, indicating that these symptoms were particularly persistent over time. Within-group cross-symptom effects were also observed: adolescent suicidal ideation predicted later sad mood, anhedonia, and sleep problems, while maternal fatigue and guilt predicted subsequent anhedonia and appetite problems, and maternal psychomotor changes predicted later suicidal ideation. Intergenerational pathways were identified whereby maternal psychomotor symptoms at T1 predicted adolescent psychomotor symptoms at T2 (<i>β</i> = 0.11), and maternal depressed mood predicted adolescent sleep problems (<i>β</i> = 0.10), with a reverse pathway from adolescent guilt to maternal guilt (<i>β</i> = 0.08).</p> Conclusions <p>Depressive symptoms in mothers and adolescents are maintained through temporally stable and cross-activating symptoms within individuals, and transmitted across generations through specific symptom-to-symptom pathways. These findings refine theoretical understanding of how depressive symptoms persists and spreads in families and highlight key symptoms as promising targets for future research and preventive efforts.</p>