Government data shows a total of 462 Armed Forces personnel have sought out "at least one" COVID-related appointment at a special rehabilitation centre.
Of the military staff seeking help, 447 had a check-up via a COVID outpatient appointment, and 260 attended a Defence COVID Recovery Service appointment.
Another form of support, a COVID course appointment, was provided to 224 members of the Armed Forces, and 26 had a course review appointment.
However, the Ministry of Defence is unable to provide an accurate record of military personnel who are on long-term sick leave because of long COVID.
The numbers asking for rehabilitation support were described as "deeply concerning" by Liberal Democrat MP Layla Moran, who called on the Government to share the figures.
Oxford West and Abingdon MP Ms Moran, who chairs the All-Party Parliamentary Group on Coronavirus, said: "These striking figures add to an already concerning picture of the shadow being cast by long COVID over our Armed Forces – the total inadequacy of the Government’s response to the rise of this condition so far is plain to see.
Watch: A look behind the scenes at the military's COVID rehabilitation centre at the Defence Medical Rehabilitation Centre at Stanford Hall.
"We rely on our Armed Forces for our protection, so it's deeply concerning to hear that such numbers have been living with this often life-limiting condition.
"With personnel numbers already cut back so far in recent years, we can't afford to let long COVID add to that any further.
"An urgent strategy is needed to respond to the threat posed by long COVID and provide support to the thousands of people suffering from the long-term consequences of this pandemic."
Long COVID is the name for several groups of symptoms experienced in the weeks and months after the immediate infection of COVID-19.
These can include fatigue, shortness of breath, chest pain, "brain fog", heart palpitations, and joint pain, among other symptoms, according to the NHS.
Ms Moran wrote to Defence Secretary Ben Wallace earlier this month, asking "how many and what proportion of military personnel referred for treatment for long COVID at the Defence Medical Rehabilitation Centre" have been treated, and have returned to work.
In reply, defence minister Leo Docherty wrote: "Between April 23 2020 and July 19 2021, the latest period for which figures are available, a total of 462 UK Armed Forces personnel had at least one appointment at one of the COVID clinics at the Defence Medical Rehabilitation Centre (DMRC).
"Of these, 447 personnel attended a COVID outpatient appointment, 260 attended a Defence Covid Recovery Service appointment, 224 a COVID course appointment and 26 a COVID course review appointment."
He added: "Information about sickness absence in the Armed Forces is not held centrally. It is therefore not possible to provide with accuracy the number of personnel who have returned to work after attending a DMRC Covid clinic."