Plants have evolved highly efficient strategies to maintain iron (Fe) homeostasis. In this study, we investigate the impact of arbuscular mycorrhizal (AM) symbiosis on the Fe-deficiency response and ionomic profile of tomato plants, as well as how Fe availability affects AM symbiosis. Fe deficiency and AM colonization both reduced shoot Fe concentrations, while root Fe concentrations increased in AM plants. Notably, Fe accumulated in cortical cells colonized by arbuscules, suggesting that in the Rhizophagus irregularis-tomato symbiosis, the fungus acts as a sink for Fe. We further show that Fe deficiency reduces expression of AM-related tomato genes ( SlEXO84, SlRAM1, SlAMT2.2 and SlPT4,) and of the fungal RiEF1α gene. These findings indicate that Fe availability is crucial for sustaining AM colonization and symbiotic functionality. Under Fe-limiting conditions, AM symbiosis enhances the Strategy I Fe acquisition pathway ( SlFRO1, SlIRT1), an effect not observed under Fe-sufficient conditions. The high Fe demand of AM symbiosis is supported by the reduced expression of the vacuolar Fe transporters SlVIT1 and SlVTL1 in mycorrhizal roots. Ionomic analysis reveals that AM colonization partially mitigates the alterations induced by Fe deficiency, underscoring the role of AM in buffering nutrient imbalances and maintaining a more stable ionomic profile under Fe stress.