In most terrestrial ecosystems nitrogen (N) is the primary limiting nutrient for plant growth. Plants interact with multiple root infecting and free living symbionts to meet their need of mineral N. However, most studies only considered single plant mutualists. This may underestimate mutualistic interactions, since roots interact with a number of symbionts potentially complementing each other to the benefit of the plant. The objective of our work was to investigate if AM fungi (Glomus intraradices) and protozoa (Acanthamoeba castellanii) complement each other in fostering N acquisition of plants (Plantago lanceolata) from organic residues (OR) in soil. To achieve this, we combined gnotobiotic cultures and stable isotope labelling (13C and 15N). Separately protozoa and AM only slightly increased plant N uptake and plant growth. In contrast, the presence of both AM and protozoa strongly increased plant N acquisition from OR, resulting in a twofold increase in plant N and an almost threefold increase in plant biomass. Our results call for more holistic approaches to understand the full potential of symbiotic rhizosphere interactions and their functioning in plant nutrition.