East Camp in St Athan, Vale of Glamorgan, will house 50 people by the end of March with more arriving in April, the Ministry of Defence said.
The site can host a maximum of 180 people.
Those arriving are eligible under the Afghan Relocations and Assistance Policy (Arap) programme.
The scheme is for those who worked for or with the UK government in Afghanistan in “exposed or meaningful” roles.
It is aimed at those who could face retribution by the Taliban, which re-took power in Afghanistan in August 2021, due to their association with international forces.
Colonel Sion Walker is in charge of the site and told the BBC Radio 4 Today programme that it would be Afghan families on the site.
“The first group are there now at St Athan awaiting for more permanent accommodation in the not too distant future.
“We are working on a timeline of about six to eight weeks, bringing the families in and we help them set up things like bank accounts and other things they need to actually live in the UK, noting that these are people who are entitled to be here and to settle here.
So we give them all the bits and pieces they need to actually settle and at the same time we’re then looking for appropriate accommodation.
He added that up until just before Christmas the site was a technical training site used by the RAF so the accommodation there is made up of two person rooms which have now been repurposed to make them more suitable for families living there.
“We owe a debt of gratitude to those brave Afghans who risked their lives working alongside our forces in support of the UK mission,” the MoD said.
Those eligible will be housed at East Camp for six weeks “before moving to more settled accommodation”, a spokesman added.
The MoD said it was working with the Welsh government and Vale of Glamorgan council to ensure the project was managed “with everybody in mind”, especially those who live locally.
Andrew Fox, a retired army officer, helped about 3,000 people to evacuate Afghanistan to the UK and other countries.
He said the programme was designed for people who worked with the British in Afghanistan who are now at risk.
“They include the Afghan national army special forces, but also a variety of contractors and interpreters and other people who were side by side with us on the frontlines, who now need to be rescued because the Taliban will kill them if they catch them.
“There’s been reports of torture, murder, and so we’re doing morally the right thing, and we’re bringing them to the UK, where they can live a life of safety, and be part of British society and stand side by side with us here again in our own country.”
Mr Fox did three tours of the country between 2007 and 2010 and said the situation was not ideal but that it was “repaying a debt”.
“I wish we could put them straight into houses, and that there was the capacity to do that here, but there isn’t, the important thing is that we’re getting that backlog in Pakistan moving because it’s an awful thing for these people to be stuck in limbo.
“Can you imagine putting your life on hold for 12, 24, maybe 36 months, where you’re waiting for someone to move you and or your family to a whole new country, where you don’t know the culture, you don’t know the language that well, and the mental strain on these people is horrendous.
“I’m just really glad that we finally got that moving.”
In 2023, plans to house Ukrainian refugees at nearby Llantwit Major drew demonstrations from a far-right group.
The Welsh government said the programme was the responsibility of the MoD, which it said it was “working constructively with” to ensure those relocated to Wales from Afghanistan were “able to integrate effectively”.