Aims: This study was performed to explore the compatibility and applicability of plant beneficial micro-organisms (i.e. Trichoderma harzianum MUCL 29707 and Glomus sp. MUCL 41833) co-entrapped in alginate beads. Methods and Results: Spores of Glomus sp. and conidia of T. harzianum were immobilized in alginate beads and the impacts of the saprotrophic fungi on the presymbiotic and symbiotic phase of the arbuscular mycorrhizal (AM) fungi evaluated under strict in vitro culture conditions. Our results demonstrated the capacity of both micro-organisms in combination to regrowth outside the calcium alginate coating. The presence of T. harzianum did not hinder the AM fungal development but rather stimulated its spore production and fitness. Conclusions: The combination of T. harzianum MUCL 29707 with Glomus sp. MUCL 41833 in alginate beads may represent a reliable alternative inoculum formulation for application in sustainable agriculture. Significance and Impact of the Study: The entrapment in the alginate beads of two fungi (i.e. a saprotroph and a symbiont) having beneficial effects on plants represents a promising formulation for the development of inoculants adapted to field application.