Proteinuria is a widely used biomarker for risk stratification in hypertensive pregnancies, with potential predictive value for adverse maternal and perinatal outcomes. This study evaluated the predictive value of 24-hour urine protein levels for adverse maternal and perinatal outcomes in hypertensive pregnancies. A retrospective cohort of 213 pregnant women with hypertension was categorized into four groups based on proteinuria severity: 2000 mg (n = 19). Higher proteinuria levels were significantly associated with increased rates of oligohydramnios (p = 0.001) and fetal growth restriction (FGR; p = 0.005), particularly in the > 2000 mg group (44.0% and 68.4%, respectively). Gestational age at delivery decreased with worsening proteinuria (p < 0.001), with the lowest mean age (32.84 ± 3.82 weeks) in the > 2000 mg group. Postpartum hospital stays were prolonged in chronic hypertension (p = 0.002) and severe proteinuria groups (p = 0.007). ROC analysis identified a 24-hour urine protein cutoff of 135 mg (AUC: 0.635, p = 0.001) for predicting fetal distress. The > 2000 mg group had universal magnesium sulfate use, earlier deliveries, and higher FGR rates. Chronic hypertension correlated with longer postpartum stays (p = 0.002) and higher postpartum renal disease (p = 0.040). These findings underscore proteinuria as a prognostic marker for adverse outcomes, supporting its role in risk stratification for hypertensive pregnancies. Future research should validate thresholds and explore targeted interventions.