The United Nations children's support agency UNICEF says it estimates 26,000 children have been affected by last week's extreme floods.
It says many of those affected are from the poorest areas of the capital Honiara and many are living in rural areas and settlements which have not yet been reached because of damage to bridges and roads.
The agency says children are especially susceptible to disease due to a lack of food and weak immune systems.
It says they have also suffered huge trauma and will need intense support.
UNICEF New Zealand is calling for 400,000 US dollars in urgent funds to help children in the aftermath of the floods.