YoungDementia UK, which supports people with early onset dementia and their families, has become part of Dementia UK, the organisations have announced.
The charities said they had been working closely together in recent years and began looking into the possibility of a merger in the summer.
A spokesman said all eight of YoungDementia UK’s staff had transferred to Dementia UK, which has 139 staff plus almost 300 specialist Admiral Nurses.
The charities said the merger would enable them to provide a stronger voice for people affected by dementia under the age of 65.
Dr Hilda Hayo, chief executive of Dementia UK, said: “Dementia UK and YoungDementia UK have worked together successfully for years and this is an excellent development, and natural progression, for both charities.
“Now, more than ever, families impacted by dementia need empathetic, specialist support, and the coming together of these two charities will greatly expand our knowledge, expertise and capability for supporting families facing young onset dementia.”
Tessa Gutteridge, director of YoungDementia UK, said: “Joining forces with Dementia UK will help us amplify the voices of those dealing with this difficult condition, and reach even more people with specialist advice and support.”
One YoungDementia UK trustee has joined the Dementia UK board and the spokesman said there were ongoing conversations about the involvement of others.