Hericium erinaceus–derived peptides have been found to exhibit various bioactivities, including immunoregulatory properties. This study investigated the transport, absorption, and potential immunomodulatory activities of a new peptide, Leu-Pro-Gly-Lys-Val-Ile-Ala-Ser (LPGKVIAS), derived from H. erinaceus. Transport and absorption of LPGKVIAS were analyzed by near-infrared fluorescence in vivo imaging in mice injected with a fluorescence probe–labeled LPGKVIAS. RNA sequencing was used to explore the immunological effects of the peptide on mouse splenocytes. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that LPGKVAS upregulated differentially expressed genes involved in immune regulation. Notably, activation of the lysosome–phagosome pathway in splenocytes of mice treated with LPGKVIAS was identified as a crucial immune defense mechanism against pathogen infection. Furthermore, reverse transcription–polymerase chain reaction studies validated the gene expression data, supporting the potential application of the peptide LPGKVIAS as an immunomodulator.