This paper details the development and application of a novel pressure-tight sampler with a metal seal capable of acquiring high-purity fluid samples from deep-sea hydrothermal vents. The sampler has a titanium diaphragm valve for sampling and a flexible titanium foil bag to store the fluid sample. Hence, all parts of the sampler in contact with the sample are made of titanium without elastomer O-ring seals to minimize the organic carbon blank of the sampler, which makes it suitable for collecting organic samples. A pressure-tight structure was specially designed to maintain the sample at in-situ pressure during the recovery of the sampler. The sampler has been successfully tested in a sea trial from November 2018 to March 2019, and pressure-tight hydrothermal fluid samples have been collected.