The current checklist presents species diversity of the order Blenniiformes in most parts of the Northwest Indian Ocean (NIO) and encompassing the marine waters of the Persian Gulf, Sea of Oman/Oman Sea, Arabian Sea, Red Sea and the Gulf of Aden. This updated checklist enumerates 81 species, representing 28 genera and two families. The family Blenniidae/ combtooth blennies present 25 genera and 64 species. Within this family, the genera Ecsenius and Istiblennius, each with seven species (8.64%), and the genus Antennablennius with six species (7.40%), comprise ranks first and second in terms of species diversity. The other 11 genera comprise one species each (1.24%). In the family Tripterygiidae/ triplefin blennies, the genus Enneapterygius presents 11 species (13.58%), Helcogramma 5 species (6.17%) and Norfolkia one species 1.24%. During the last 12 years, only three new species Adelotremus leptus, Enneapterygius qirmiz and Entomacrodus solus have been described from the region. Species diversity of both families in the Persian Gulf is lower than in the Oman, Arabian and Red Seas due to substantial variations in the environmental features and oceanographic characteristics of the Persian Gulf (e.g., sea surface temperature ranges (12-36°C), high salinity (>45), low depth (90-100 m), closed geographic position and its geological history during the glaciation in Pleistocene. Based on the IUCN red list, most of the reported species (75 species, 92.6%) have been rated as least concern (LC), two species (Oman ypsibn and Omobranchas mekranensis) are listed in the vulnerable (VU), and Entomacrodus solus is considered as endangered (EN). Ongoing research and intensive collections will likely reveal additional species in the northwest Indian Ocean.