Abundance and diversity of man-biting mosquito species in the tropical rainforest belt of Southeastern Nigeria was undertaken in three selected communities. The study lasted 12 months cutting across wet and dry seasons. Adult mosquitoes were collected, both indoors and outdoors, using pyrethrum spreadsheet method (PSC) and human landing catch technique (HLC). The mosquitoes were morphologically identified using identification guides, later confirmed by expert taxonomists. Data were analyzed using statistical package for Social Sciences (SPSS version 21.0) Percentages were used to determine relative abundance of the mosquitoes. Species richness was determined using Shannon-Weiner Indices. A total of 4,434 adult mosquitoes consisting of 936 (21.11%) indoors and 3,498 (78.89%) outdoors were collected. The mosquito collections were made of 15 species belonging to six genera. Aedes mosquitoes 3,072 (69.28%) significantly topped the list of the mosquito population (P < 0.05) and was the most abundant species caught outdoors. Anopheles mosquitoes 627 (14.14%) were significantly higher indoors (P < 0.05) than all the mosquitoes collected. Monthly abundance of the mosquitoes showed a bi-modal peak with a minor peak occurring in June and a major peak in October. In the dry season, mosquito abundance in the three communities was similar, but differed significantly (P < 0.05) during the wet season. Shannon-Weiner Indices ranked Okija community as the most diverse in species richness. The preponderance of Anopheles, Culex and Aedes species in the study area was viewed as a danger signal against mosquito-borne diseases transmission as the collected species are proven vectors of public health diseases. Health education is advocated for protection and improvement of the people’s health.