Mycorrhizas are considered bio-fertilizers that could improve plant growth when seedlings are inoculated. This study assessed how the interactions between chemical fertilization levels and arbuscular mycorrhizal fungus species (AMF) affected the seedling's morphology and physiology traits. In addition, we evaluated the subsequent effect on plant quality of Prosopis alba. The impact on the seedling's growth in the nursery was evaluated by applying different chemical fertilization concentrations (0, 30, 60 and 100%). Subsequently, the seedlings were inoculated or not with a mixture of native AMF from two origins of contrasting sites in the Chaco Region. We measured biochemical traits (chlorophylls and carotenoid contents) and morphological parameters (stem neck diameter, shoot height, root dry weight, aerial dry weight). The mycorrhizal response on P. alba seedlings was calculated from these variables. Our results suggest that mycorrhizal response on stem neck diameter was significantly higher in the treatment inoculated with both AMF at 60% fertilizer concentration. In inoculated treatments, the shoot height was significantly higher (p <0.0001) than in control treatments. The aerial dry weight exhibited no differences between treatments. The root dry weight exhibited differences between inoculated and control treatments, showing higher values in control seedlings. We found a negative mycorrhizal response on the biochemical parameters, as control treatments showed higher pigments concentration than inoculated plants. Preliminarily, we observed a positive mycorrhizal response to the AMF in interaction with chemical fertilization (at 60% fertilizer concentration). These results were reflected mainly over some morphological parameters than over biochemical parameters. The lack of a clear answer is probably since the benefits of the symbiosis on the host plant could be observed in the establishment phase in the field.