The figure for 2020 was lower than the 543 suicides in 2018.
Defense Secretary Lloyd Austin called the new numbers "troubling," and said suicide prevention is "a paramount challenge" for the military.
"Suicide rates among our service members and military families are still too high, and the trends are not going in the right direction," Austin said in a statement Thursday.
"We must redouble our efforts to provide all of our people with the care and the resources they need, to reduce stigmas and barriers to care, and to ensure that our community uses simple safety measures and precautions to reduce the risk of future tragedies."
He added that the Pentagon will "continue to work swiftly and urgently," in collaboration with the Department of Veterans Affairs.
USA Today was the first to report the new statistics before these were made public.
Alaska has been the site of several suicides, according to USA Today, with six suicides in the first five months of the year. The newspaper reported that the Army has spent more than US$200 million in an attempt to improve the quality of life at its bases in the state.
A study released in June this year uncovered that more than 30,000 active-duty personnel and veterans of wars that followed the September 11, 2001, terrorist attacks had committed suicide.
That number, the study noted, was almost three times as many service members who were killed in post-9/11 war operations.
Earlier in September 2021 the Department of Veteran Affairs released a report that said veteran suicides in 2019 dropped to its lowest levels observed over the previous 12 years.
