The establishment of the potential vector species Aedes (Finlaya) japonicus japonicus (Theobald) (Diptera: Culicidae) in southern Belgium is reported. The species was most likely introduced through the international trade in used tires. It was first collected in 2002 on the premises of a second-hand tire company and was sampled using different sampling methods in the two consecutive years (2003–2004). It was only in 2007 and 2008, during a national mosquito survey (MODIRISK), that its presence as adults and larvae at the above-mentioned site and at another tire company in the area was confirmed based on morphological and molecular identification. This discovery is the first record for Belgium of an exotic mosquito species that established successfully and raises the question on the need for monitoring and control. Considering the accompanying species found during the surveys, we also report here the first observation of Culex (Maillotia) hortensis hortensis (Ficalbi) in Belgium.