Herein the flapjack octopods (Opisthoteuthidae) of northwestern Australia in addition to adjacent Indonesian waters are examined. Three species are identified, all distinct from taxa recorded off southern and southeastern Australia in the preceding Part I contribution. A new species in genus Opisthoteuthis, O. carnarvonensis sp. nov., is described from five specimens collected off northwestern Australia. Opisthoteuthis cf. philipii is described from off northwestern Australia (single specimen) and Indonesian waters (seven specimens). Lastly, a partial re-description is provided for O. extensa, which is transferred to genus Insigniteuthis (comb. nov.) and has its range extended to Java and northwestern Australia, the male of I. extensa is shown to be comparable to I. dongshaensis in enlarged sucker configuration. A key is proposed to enable the identification of Opisthoteuthidae globally.