AbstractIntroductionSoil microplastic (MP) pollution has emerged as a main factor of global change, but its effects on soil nutrient availability and uptake by crops (macro and micronutrients) are largely unknown. Arbuscular mycorrhizal fungi (AMF) are regulators of nutrient availability and uptake and can interact with soil MP.Materials and MethodsBuilding on previous studies, here we explored in a 50‐days pot experiment the influence and interaction of MP fibres (0.4%) and commercial AMF in soil and onion chemistry, that is, in elemental composition of onion shoots and soils (C, N, Ca, Mg, K, P, S, Cu, Fe, Mn and Zn) and micronutrient soil availability (Cu, Fe, Mn and Zn).ResultsMP had detrimental effects on K, Mg and S, but increased the soil availability of Zn and shoot uptake. AMF inoculation buffered the effects of MP by balancing/enhancing nutrient availability and plant uptake. Particularly, the commercial AMF inoculum remarkably enhanced Mn uptake by onion.ConclusionOur results support the use of AMF to sustainably manage agricultural ecosystems contaminated with MP, buffering and counteracting the effects of MP by balancing nutrient availability and plant uptake.