The vehicle, which contained some foodstuffs and medical supplies for refugees, disappeared from outside an International Aid Trust store in Chorley on Sunday night.
Charity officials say the Luton van was filled mainly with second hand furniture which was ready to be delivered to customers in the Lancashire area to raise cash for the aid operation in eastern Europe.
"But there were also some bags and boxes of tinned and dried food, as well as things like bandages, plasters and sanitary products, which had been donated and would have been going out on one of our shipments to refugees," said furniture store manager Dean Higham.
"It's a massive blow. Not only have we lost all the things inside the van, but we've lost the van as well which has had a huge effect on our work here."
Police are studying CCTV footage from a neighbouring shop which shows people arrive in a smaller van and, within three minutes, drive off in the charity vehicle.
It is thought the thieves used an electronic device to gain entry to the van because all the vehicle's keys were locked away inside the building at Croft Mill in Pall Mall.
"I think it's been stolen to order," said Dean. "They were an away in quick time and it doesn't look like they did any damage to get into the van.
"Presumably they won't want the contents, so they will probably just dump them.
"It's frustrating and it's costly. There was a full tank of fuel in the vehicle ready for going out on deliveries on Monday. The furniture in there was worth around £1,000 - all money that had been paid which will now have to be refunded.
"We are a charity, for goodness sake. We are reliant on donations of furniture that we can sell to raise money. And the other things were in there had been picked up from our drop-off points and were due to be taken to our main base to go on trailers to be driven abroad.
"We have sent out 11 trailers so far and we are working hard to send even more. This has really set us back."
Anyone with information about the theft should contact police.