The cash is aimed at ensuring a "seamlessly managed transition" from child to adult mental health services.
Health Secretary Vaughan Gething said he hoped the extra funding would make "a real and positive difference".
The money is on top of £1.25m already spent on treating eating disorders in people of all ages in Wales.
While child and adolescent mental health services (CAMHS) involve families in the treatment of eating disorders up to the age of 18, treatment models for adults may not always include the family.
The new money will pay for training and extra support from specialist staff, and ease the transition to adult services.
"Eating disorders comprise a range of highly complex mental illnesses, as well as being physically debilitating conditions in themselves, which is why early diagnosis and intervention is vital," said Mr Gething.
"The additional funding I'm announcing today will help ensure the services and treatment approach young people and their families receive will not change when they transition from CAMHS into adult services.
"This will help ensure young people receive the care and support they need during what is an extremely difficult time for them and their family.
"I hope the improvements this funding will support will make a real and positive difference to them."
Young people with eating disorders in Wales will get more help as they turn 18 with an extra £500,000 a year of funding.