Autism Guernsey has failed to secure a Children in Need grant for 2025 and it relies on this to provide services for 130 island youngsters and their families.
Autism Guernsey has received a grant from Children in Need for the past eight years.
Its application for next year was turned down because Children in Need says it had less money to give, and competition regionally was strong.
The new chair of Autism Guernsey, Dave Harry, says he is grateful for their support in the past, but unless money can be found quickly, then services for 130 youngsters will end in December:
"Proper social communication, interaction, imagining things. These are the things we do for youngsters as part of the funding from Children in Need, and with that funding stopping, we won't be able to do that come 1st January."
Autism Guernsey offers support in the form of groups and social clubs and activities across the summer.
Dave Harry says these also benefit the parents and carers of autistic youngsters, but warns they may have to end, as they won't have money to pay salaries:
"We won't have the ability to provide those, because we won't have the funding to employ the people to do that work."
He says it is now time to organise a more sustainable funding model:
"We really do need to try to get something in place which will provide us with a safety net, so that if somebody does pull out, we will not find ourselves in the position that we are in now."