This study explores the sustainable management of agricultural waste through the transformation of spoiled eggs into high-quality liquid fertilizers. Egg-based fertilizers (EFs) prepared from different input compositions were characterized physicochemical properties and evaluated effect on the growth, physiological performance, and yield of Malabar spinach (Basella alba). Three treatments were prepared: EF1 (spoiled eggs without chicks), EF2 (spoiled eggs with chicks), and EF3 (a 1:1 mixture of both). EF1 contained the highest concentrations of total nitrogen (6.09 g L⁻¹), total and available phosphorus (1.05 g L⁻¹ and 0.80 g L⁻¹ P₂O₅, respectively), and total calcium (3.79 g L⁻¹ CaO), with no detectable Escherichia coli or Salmonella. EF3 had the highest potassium content (1.16 g L⁻¹ total and 1.04 g L⁻¹ available K₂O). In a field trial, EF1 was applied at concentrations of 10‰, 15‰, and 20‰, and compared with a commercial organic fish fertilizer and an unfertilized control. Application of EF1 at 15‰ significantly improved shoot length, leaf dimensions, SPAD, leaf area index (LAI), and yield (6.3 and 11.9 t ha⁻¹ at 21 and 37 days after planting, respectively). Yield was strongly correlated with leaf length (r = 0.96**), leaf width (r = 0.92**), SPAD (r = 0.84**), and LAI (r = 0.90**), underscoring the importance of leaf expansion and chlorophyll content in determining productivity. Nitrate concentrations in all treatments remained below 150 mg kg⁻¹, well within safe limits for leafy vegetables. These findings highlight EF1 at 15‰ as a safe, effective, and sustainable fertilizer option for leafy vegetable production.