| Summary: | <i>Purpureocillium lavendulum</i> is a fungus with promising biocontrol applications. Here, transcriptome data acquired during the infection of <i>Caenorhabditis elegans</i> by <i>Purpureocillium lavendulum</i> showed that the transcription of metabolite synthesis genes was significantly up-regulated after 24 and 48 h of the fungus-nematode interaction. Then, the up-regulated transcription level of lipoxygenase was confirmed by RT-qPCR. The ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis of differential metabolites revealed that this interaction resulted in the emergence of new metabolites or enhanced the production of metabolites. The results of the UPLC-MS analysis and the nematicidal assay were used to establish optimal culturing conditions under which 12 metabolites, including 3 hydroxylated C<sub>18</sub> fatty acids and 9 steroids, were isolated and identified. Among them, hydroxylated fatty acids showed pronounced nematicidal activity against <i>Meloidogyne incognita</i>, and two degradative sterols showed chemotaxis activity to <i>M</i><i>. incognita</i>. This study lays a foundation for the function of lipoxygenase and its products during the infection of <i>Purpureocillium lavendulum</i>.
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