ABSTRACT In the banana production system, a sustainable alternative for producing quality plantlets would be inoculation with plant growth-promoting bacteria (PGPB). Therefore, this study aimed to evaluate the growth-promoting potential of a bacterial biomass in micropropagated banana plantlets cultivar Prata Catarina, and to identify the mechanisms involved in plant-microorganism interactions. In vitro, the biochemical assays tested were the solubilisation of phosphates, production of enzymes, production of ammonia, siderophores, and indole acetic acid. In the in vivo tests, the plants were bacterised (109CFU mL-1) in two phases: acclimatisation, and cultivation in plastic bags. The design was a randomised block with 9 and 7 repetitions per treatment, which were: T1: control; T2: plants treated with isolate E2 (Bacillus pumilus group); T3: plants treated with RAB9 isolate (B. pumilus) for each phase. Bacterial isolates were capable of producing cellulases, amylases, pectinases, lipases, proteases, and siderophores. The plants gained in height, root length, root dry mass, pseudostem diameter, and leaf area. It is concluded that the PGPB can promote the growth of micropropagated banana plantlets through the production of enzymes and siderophores.