Background and aims <p>Brace roots are crucial for stalk anchorage and plant growth, yet the effects of soil compaction and moisture conditions on their development remain unclear. This study examined the interactive effects of soil compaction and moisture on maize brace root traits and explored the associated hormonal regulatory mechanisms.</p> Methods <p>A completely randomized design was employed with two factors: soil bulk density (1.2&#xa0;g&#xa0;cm⁻³, uncompact, B_1.2; and 1.5&#xa0;g&#xa0;cm⁻³, compacted, B_1.5) and soil water content (75% and 100% field capacity, W₇₅ and W₁₀₀). Brace root traits, hormone content in nodal tissue, and soil properties were analyzed.</p> Results <p>Higher soil water content increased brace root node number (BRNN), spread width (BRSW), and diameter (BRD), whereas soil compaction increased brace root angle (BRA). Nodal 1-aminocyclopropane-1-carboxylic acid (ACC) was positively correlated with BRNN, BRSW, and BRD, suggesting a positive regulatory role of ethylene in brace root development. Cytokinins (CKs) were negatively associated with brace root development, whereas indole-3-acetic acid (IAA) had minimal effect. The higher nodal ACC observed under wetter conditions may be linked to changes in soil gas diffusivity.</p> Conclusion <p>These findings indicate that compacted and wet soils enhance brace root development via ethylene regulation, offering a potential strategy to manage soil physical conditions for improved lodging resistance and nutrient acquisition in maize.</p>