Aluminum phytotoxicity in acid soils is an important environmental stress that negatively affects crop production, but arbuscular mycorrhizal (AM) fungi performance would allow plants to better withstand this environmental condition. This study aimed to analyze the effect of soil Al on early AM colonization of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) cultivars. Near-isogenic Crac, Invento, and Porfiado wheat cultivars and Sebastián and Aurora barley cultivars were sown in pots in an acid soil at three Al saturation levels (60, 34, and 11%). At 20 d after sowing (DAS) &rsquo;Crac&rsquo; presented higher AM colonization (27%) than other cultivars. However, &rsquo;Invento&rsquo; had the fastest colonization at 41 DAS, which was inhibited in short term at lower Al-saturation. Moreover, roots of &rsquo;Aurora&rsquo; were colonized 28 and 51% at 20 and 66 DAS, respectively, and also decreased at lower Al-saturation. In soil with 60% Al-saturation a great spore production was observed at 41 DAS, &rsquo;Aurora&rsquo; had the highest spore density at 66 DAS. At 20 DAS a negative relationship (r = -0.37; p < 0.001) was observed between the early root colonization and root weight. In addition, such relation was stronger (r = -0.49; p < 0.001) when plants were grown at high Al saturation. An early AM colonization was observed in all cultivars essayed when growing at high Al saturation being higher in cultivars apparently more Al tolerant, suggesting that an early AM colonization can be an important factor in Al tolerance for agricultural plants cropped in acid soils.