Magnetosome-producing microorganisms can sense and move toward the redox gradient and have been extensively studied in terrestrial and shallow marine sediment environments. However, given the difficulty of sampling, magnetotactic bacteria (MTB) are poorly explored in deep-sea hydrothermal fields. In this study, a deep-sea hydrothermal vent chimney from the Southern Mariana Trough was collected using a remotely operated submersible. The mineralogical and geochemical characterization of the vent chimney sample showed an internal iron redox gradient. Additionally, the electron microscopy of particles collected by magnetic separation from the chimney sample revealed MTB cells with bullet-shaped magnetosomes, and there were minor occurrences of cuboctahedral and hexagonal prismatic magnetosomes. Genome-resolved metagenomic analysis was performed to identify microorganisms that formed magnetosomes. A metagenome-assembled genome (MAG) affiliated withNitrospinaehad magnetosome genes such asmamA, mamI, mamM, mamP, andmamQ. Furthermore, a diagnostic feature of MTB genomes, such as magnetosome gene clusters (MGCs), includingmamA, mamP, andmamQ, was also confirmed in theNitrospinae-affiliated MAG. Two lines of evidence support the occurrence of MTB in a deep-sea, inactive hydrothermal vent environment.