Cadmium (Cd) contamination of agricultural soils poses serious threats to food security. While layered double hydroxides (LDHs) have been widely used for the chemical immobilization of Cd, their potential to simultaneously incorporate a competitive uptake mechanism within a single material remains unexplored. In this study, MnFe-LDHs were prepared with Mn and Fe at molar ratios of 1: 1 (MF11) and 1: 2 (MF12) via co-precipitation. Pot experiments were conducted to investigate the effect of MnFe-LDHs addition on Cd migration and transformation in the soil-plant system and the underlying mechanism. The results showed that MnFe-LDHs reduced soil available Cd by 2.8 %-24.3 % through interlayer-specific adsorption, ion exchange, and surface hydroxyl complexation. Meanwhile, exchangeable Cd was transformed into more stable carbonate-bound and Fe-Mn oxide-bound upon MnFe-LDHs addition. Moreover, MnFe-LDHs underwent partial structural dissolution under soil conditions, triggering the reductive dissolution of Mn and leading to a 13.6 %-125.5 % increase in bioavailable Mn, which in turn enhanced Mn and Cd competition at the root interface and reduced the grain Cd accumulation by 26.9 %-68.9 %. Overall, MF11 outperformed MF12, showing greater potential for practical application. This study develops a new material with a dual-action mechanism of chemical immobilization and competitive uptake, providing a promising strategy to produce Cd-safe, Mn-enriched wheat in contaminated alkaline soils.