Arsenic (As) mobility in soils is strongly influenced by iron (Fe) redox transformations and dissolved organic matter (DOM) dynamics, yet the combined effects of ferrihydrite-compost composites (Fh-CC) under fluctuating soil redox conditions remain poorly understood. A microcosm experiment with varying redox conditions was conducted to investigate the effects of Fh-CC on As fate from texturally different soils of Bangladesh (sandy loam) and Pakistan (sandy clay loam). Results demonstrated that Fh-CC application increased dissolved Fe by 62.2% and 81.0% while decreased dissolved As contents by 34.9% and 51.9% under oxidized conditions, from sandy loam and sandy clay loam soil, respectively. Under reduced conditions, Fh-CC increased dissolved Fe by 13% and 58.8% however dissolved As contents were decreased by 69.9 and 70.4% in sandy loam and sandy clay loam soil, respectively. Fh-CC application enhanced the soil organic carbon contents by 154% and 81.8% in sandy loam and sandy clay loam soil, respectively. Spectroscopic analyses (3D-EEM and FTIR) demonstrated that Fh-CC amendment enriched fulvic and humic acid-like DOM fractions and, through the identification of Fe-O/Fe-OH bands, provided direct evidence for active Fe redox cycling and intensified Fe-DOM complexation. Under reduced conditions, Fh-CC amendment significantly stimulated extracellular enzyme activities across contrasting soil textures, reflecting a marked enhancement in microbial metabolic activity. These results demonstrate that Fh-CC-driven Fe transformation and DOM interactions regulate As mobility, with reduced conditions promoting stronger Fe-associated As stabilization.