Knowledge of Afrotropical bat diversity is hindered by hidden diversity because of inefficient sampling techniques, limited survey effort, and taxonomic description. With 90 bat species recorded, Nigeria supports almost a third of the bat diversity known to occur in Africa, yet the country remains relatively under-sampled. Southeastern Nigeria and southwestern Cameroon are predicted to be the largest of six bat diversity hotspots in Africa, with the Cameroonian side receiving more sampling effort. This area is also recognized to support hyperdiverse mammalian assemblages and endemic species. Notwithstanding, two major protected areas on the Nigerian part of this bat diversity hotspot were hitherto not sampled, raising the likelihood of discovering new country records in these conservation priority forests. We conducted an intensive survey using harp traps and mist nets in forests of Afi Mountain Wildlife Sanctuary and Cross River National Park (Okwangwo Division). We also recorded echolocation calls of captured individuals to create the first in-country call library. We captured 36 bat species of which 10 are new country records raising the number of bat species known from Nigeria to 100. Harp trap captures represented 99% of forest understory bats sampled with 15 out of 18 species caught exclusively in traps. Rarefaction curves of captures suggest near-complete sampling with harp traps but incomplete sampling with mist nets. Eight of the 10 new country records were captured exclusively in harp traps, demonstrating the value of contemporary techniques for frequently missed species — here referred to as methodological blind-spot diversity. We report the re-identification of two museum specimens that were previously identified as Rhinolophus hillorum (R. cf. hillorum) and Miniopterus inflatus (M. villiersi) thus, our captures of the true forms confirm the presence of both species in Nigeria for the first time. We also provide noteworthy taxonomic comments on other species. To improve the efficiency of future Afrotropical bat surveys we recommend the deployment of complementary trapping techniques in identified diversity hotspots, especially sites that have been under-sampled.