<p>Pediatric pulmonary vein stenosis (PVS) is a rare, progressive condition associated with significant morbidity and mortality. While pulmonary venous decompressing collaterals (PVDC) have been described, their clinical relevance and impact on long-term outcomes remain unstudied. We aimed to characterize these collaterals and determine their association with outcomes and mortality in pediatric PVS. This was a single-center, retrospective cohort study of 64 pediatric patients (≤ 18 years) treated for PVS between 2017 and 2022. Patients with single-ventricle heart disease were excluded. PVDC were defined as contrast flow to a neighboring lobar or interlobar segment due to medial occlusion identified on serial angiograms. The primary outcome was PVS-related mortality analyzed using multivariable Cox proportional hazards models, adjusting for age and gestational age. PVDC were present in 39/64 (61%) patients. The presence of collaterals was significantly associated with lower all-cause (15% vs. 40%, <i>p</i> = 0.027) and PVS-related mortality (13% vs. 40%, <i>p</i> = 0.012). This benefit was most pronounced in the bilateral disease subgroup (45% of the cohort). In this group, patients with collaterals had significantly lower PVS-related mortality (15% vs. 78%, <i>p</i> = 0.002) and lower indexed pulmonary vascular resistance (iPVR 3.2 vs. 7.6 Wood unit x m², <i>p</i> = 0.006). In the adjusted Cox model, collateral presence in bilateral PVS was strongly associated with improved survival (HR 0.09, 95% CI: 0.02–0.46, <i>p</i> = 0.003). In conclusion, pulmonary venous decompressing collaterals are a favorable adaptive mechanism in pediatric PVS. Their presence is associated with improved survival, particularly in high-risk patients with bilateral disease. These findings emphasize the importance of integrating collateral status into prognostic assessment and therapeutic decision-making.</p>