The class Calcarea comprises 831 (8.5%) out of the 9,700 described species of the phylum Porifera. Knowledge on the diversity and distribution of calcareous sponges remains limited due to insufficient sampling and taxonomy specialists. This is also evident in the Great Barrier Reef (GBR), which presents only 25 (9%) out of the 280 calcareous sponges reported for Australia. Therefore, this study seeks to describe the species diversity of the subclass Calcinea from Heron Island, GBR, using integrative taxonomy (morphological and molecular analyses). Among the 19 specimens analysed, eleven species were identified, seven of them being new to science: Arturia sp. nov., Clathrina sp. nov., Janusya sp. nov. 1, Janusya sp. nov. 2, Neoernsta sp. nov. 1, Neoernsta sp. nov. 2, and Neoernsta sp. nov. 3. Additionally, four previously known species had their distributions widened within the South Pacific Ocean: Arturia dubia, Clathrina fakaravae, Clathrina procumbens, and Clathrina cf. stipitata. Some of these species show trans-Pacific distributions. Knowledge on the Calcinea diversity in Heron Island rose from 4 to 15 species (275%) and from 15 to 26 (73%) in the GBR. Moreover, the endemism of Calcinea in Heron Island is now 53% (8 species) and 46% in the GBR (12 species). This study also documents the first records of the genera Arturia and Neoernsta in the GBR. These results confirm the underestimation of the diversity of Calcarea in the GBR, evidencing that more studies are needed even in well-studied locations.