This paper studies the Middle Miocene ostracods from three different outcrops in the Al Khums area, northwestern Libya. Lithologically, these outcrops belong to the Al Khums Formation, and are considered synchronous due to the great similarity in their ostracod content. Twenty seven ostracod species, belonging to 22 genera and 13 families, were identified. Although the age of the Al Khums Formation cannot be precisely constrained based on its ostracod assemblage, the presence of the larger benthic foraminiferan subspecies Borelis melo melo allows to assign to the sequence a Middle Miocene age. The identified ostracods indicate that the depositional environment was shallow marine. This conclusion is also supported by the co-occurrence of algae, large oysters and corals. Multivariate analyses were applied to the present data to distinguish the paleobiogeographical provinces of the studied ostracod species. The results indicate that there are two distinguished bioprovinces: (1) The South Tethyan bioprovince (STP) including Algeria, Libya and Egypt, and (2) The North Tethyan bioprovince (NTP) including Spain, Italy, Malta, France, Turkey and Greece. Similarities between the ostracod assemblages of these bioprovinces suggest a good marine connection between both sides of the Mediterranean Sea during the Middle Miocene.