Leucojum aestivum L. is a natural source of Amaryllidaceae alkaloids, especially galanthamine and lycorine. Galanthamine is an acetylocholinesterase inhibitor used for the treatment of Alzheimer’s disease, while lycorine may inhibit cell division. Several research works indicated that biotechnological methods using L. aestivum in vitro cultures could be alternative sources of Amaryllidaceae alkaloids for total chemical synthesis and extraction from field grown plants (Laurain-Mattar and Ptak, 2018; Ptak et al., 2019). Exploitation of that endophytic microorganism as a secondary metabolitepromoting agent is a very important strategy in the biotechnological production of bioactive compounds. We isolated the endophytic bacterium from plant cultures of L. aestivum, and basing on the data from the 16S rRNA gene sequence we identified it as Paenibacillus lautus. Subsequently, we investigated the effects of dead endophytic bacterial elicitors, used at concentrations of 0 (control), 0.01, 0.02 and 0.04% for 7, 14 and 28 days, on biomass and Amaryllidaceae alkaloid production in L. aestivum in vitro plants. Elicitation with 0.04% extract of P. lautus for 28 days stimulated the growth of L. aestivum plants. Capillary GC-MS led to the identification of five alkaloids in obtained plant materials. Their number depended on the concentration and duration of the elicitor action. The highest galanthamine (44.47 μg/g DW) and lycorine (235.73 μg/g DW) contents were observed in plants treated with 0.02% bacterial extract for 14 days. This is the first report on the isolation of P. lautus from in vitro culture of L. aestivum and the use of that endophytic bacterium as an elicitor of Amaryllidaceae alkaloid biosynthesis.