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The auxin/indole-3-acetic acid (<i>Aux/IAA</i>) and auxin response factor (<i>ARF</i>) genes are two crucial gene families in the plant auxin signaling pathway. Nonetheless, there is limited knowledge regarding the <i>Aux/IAA</i> and <i>ARF</i> gene families in <i>Populus simonii</i>. In this study, we first identified 33 putative <i>PsIAAs</i> and 35 <i>PsARFs</i> in the <i>Populus simonii</i> genome. Analysis of chromosomal location showed that the <i>PsIAAs</i> and <i>PsARFs</i> were distributed unevenly across 17 chromosomes, with the greatest abundance observed on chromosomes 2. Furthermore, based on the homology of <i>PsIAAs</i> and <i>PsARFs</i>, two phylogenetic trees were constructed, classifying 33 <i>PsIAAs</i> and 35 <i>PsARFs</i> into three subgroups each. Five pairs of <i>PsIAA</i> genes were identified as the outcome of tandem duplication, but no tandem repeat gene pairs were found in the <i>PsARF</i> family. The expression profiling of <i>PsIAAs</i> and <i>PsARFs</i> revealed that several genes exhibited upregulation in different tissues and under various stress conditions, indicating their potential key roles in plant development and stress responses. The variance in expression patterns of specific <i>PsIAAs</i> and <i>PsARFs</i> was corroborated through RT-qPCR analysis. Most importantly, we instituted that the <i>PsIAA7</i> gene, functioning as a central hub, exhibits interactions with numerous Aux/IAA and ARF proteins. Furthermore, subcellular localization findings indicate that <i>PsIAA7</i> functions as a protein localized within the nucleus. To conclude, the in-depth analysis provided in this study will contribute significantly to advancing our knowledge of the roles played by <i>PsIAA</i> and <i>PsARF</i> families in both the development of <i>P. simonii</i> tissue and its responses to stress. The insights gained will serve as a valuable asset for further inquiries into the biological functions of these gene families.