Acid sulfate soils (ASS) are characterized by extreme acidity and high aluminum toxicity, which severely restrict plant growth and nutrient availability. To address these challenges, this study evaluated the effectiveness of nano-engineered zeolite (<100 nm) and calcium humate (Ca-humate) as hybrid soil amendments for chemical remediation of ASS. The nano-zeolite was produced through high-energy ball milling of natural zeolite from Klaten, Central Java, yielding 91.41% particles <100 nm. Pot experiments were conducted using acid sulfate soils collected from Segoro Anakan Lagoon, Central Java, Indonesia, following a Completely Randomized Design with two amendment factors: nano-zeolite (6, 12, and 18 t ha⁻¹; equivalent to 14, 28, and 42 g pot⁻¹) and Ca-humate (6.88, 8.6, and 10.32 t ha⁻¹; equivalent to 16, 20, and 24 g pot⁻¹), with untreated pots as the control. Results showed that Segoro Anakan ASS had an extremely acidic pH (3.21), high Al and Na saturation, and low N and P levels. Application of nano-zeolite and Ca-humate significantly increased soil pH, cation exchange capacity (CEC), and base cations (Ca²⁺, Mg²⁺, K⁺, and Na⁺), while reducing exchangeable Al³⁺, Fe²⁺, SO₄²⁻, and pyrite content. The combined application of 12 t ha⁻¹ nano-zeolite and 10.32 t ha⁻¹ Ca-humate effectively decreased Al³⁺, Fe²⁺, SO₄²⁻, and pyrite solubility by 59.5%, 42.7%, 79.2%, and 50%, respectively. These improvements are attributed to complementary mechanisms of ion exchange, complexation, and pH buffering. The hybrid use of nano-zeolite and Ca-humate represents a promising amelioration strategy to mitigate Al and Fe toxicity and enhance macronutrient availability in tropical acid sulfate soils