Dr Al Neyadi, 41, was long overdue for a trim, having arrived at the orbiting science laboratory nearly a month ago.
He has become the longest-serving Arab astronaut in space and has five months of his mission remaining.
The Mohammed bin Rashid Space Centre shared a photo on Wednesday of Dr Al Neyadi getting his new hairdo.
"The hair trimmer, used by Sultan's colleague Nasa astronaut Frank Rubio, has a suction device which prevents hair from floating and contaminating the microgravity environment aboard the ISS," the space centre said.
Since arriving at the station on March 3, Dr Al Neyadi has been multitasking, including science experiments, harvesting tomatoes and plumbing work.
He has been studying human heart tissue as part of research that could help scientists back on Earth devise therapy and medication that could prevent people from developing heart disease.
He was also the test subject of another experiment that will help researchers study astronauts' sleep quality in space.
Dr Al Neyadi wore a sleep monitoring headband for a full day last week and then transferred the data to the European Physiology Module laptop.
"The sleep monitoring technology investigates astronauts’ sleep quality by measuring duration, sleep stages, heart rate and the number of awakenings," Nasa said.