Two new species of Begonia, Begonia holosericeoides Ardi & D. C. Thomas and B. aketajawensis Ardi & D. C. Thomas, are described from Aketajawe Lolobata National Park, Halmahera, Indonesia. The two species belong to Begonia section Petermannia. Begonia  holosericea, previously only tentatively assigned to a section, is here assigned to section Petermannia based on the examination of newly available material. Additionally, a revised description and an illustration are provided. A key to the Moluccan species of Begonia is presented.