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Phytochrome-interacting factors (PIFs) are essential for plant growth, development, and defense responses. However, research on the <i>PIFs</i> in sweet potato has been insufficient to date. In this study, we identified <i>PIF</i> genes in the cultivated hexaploid sweet potato (<i>Ipomoea batatas</i>) and its two wild relatives, <i>Ipomoea triloba</i>, and <i>Ipomoea trifida</i>. Phylogenetic analysis revealed that IbPIFs could be divided into four groups, showing the closest relationship with tomato and potato. Subsequently, the PIFs protein properties, chromosome location, gene structure, and protein interaction network were systematically analyzed. RNA-Seq and qRT-PCR analyses showed that <i>IbPIFs</i> were mainly expressed in stem, as well as had different gene expression patterns in response to various stresses. Among them, the expression of <i>IbPIF3.1</i> was strongly induced by salt, drought, H₂O₂, cold, heat, <i>Fusarium oxysporum</i> f. sp. <i>batatas</i> (<i>Fob</i>), and stem nematodes, indicating that <i>IbPIF3.1</i> might play an important role in response to abiotic and biotic stresses in sweet potato. Further research revealed that overexpression of <i>IbPIF3</i>.1 significantly enhanced drought and <i>Fusarium</i> wilt tolerance in transgenic tobacco plants. This study provides new insights for understanding PIF-mediated stress responses and lays a foundation for future investigation of sweet potato PIFs.