In February 1999 Hoshide was selected by NASDA (now JAXA) as one of three Japanese astronaut candidates for the International Space Station (ISS).

Since April 2001, he has participated in ISS Advanced Training, as well as supporting the development of the hardware and operation of the Japanese Experiment Module Kibō and the H-II Transfer Vehicle (HTV).

[3] In 2016 he served as part of the 2016 European Space Agency's Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills (CAVES) expedition.

Discovery and its crew docked to the International Space Station on 2 June 2008, beginning 8 days of operations to install the Japanese Experiment Module-Pressurised Module (JEM-PM).

On Flight Day 4, NASA astronauts Mike Fossum and Ronald Garan performed a spacewalk to prepare the ISS and the JEM-PM for installation, during this Hoshide and fellow STS-124 Mission Specialist Greg Chamitoff robotically removed the module from Discovery's payload bay and moved it to its new home on the port the side of Node 2.

[9] Following the launch of Expedition 30/31, Hoshide started training for his own flight, alongside Roscosmos cosmonaut Yuri Malenchenko and NASA astronaut Sunita Williams.

Malenchenko, Williams and Hoshide safely landed approximately six hours after undocking near the remote town of Arkalyk, Kazakhstan following 127 days in space.