Between 1995 and 2006, a total of 3280 lycaenid adults belonging to 47 species were collected in order to Study their distribution and current status in Bursa, northwestern Turkey. Of these, Tomare nogelli is a newly recorded species for northwestern Turkey. The following lycaenid species had not been seen since the 1860s: Aricia eumedon, Cupido osiris, Kretania eurypilus, Plebeius sephirus, and P. ripartii. The endemic water dock plant species Rumex olympicus was recorded as a new host for the larvae of Lycaena dispar. Both Aricia hyacinthus and the endemic Polyommatus ossmar olympicus are under threat of extinction. In contrast, the status of some Polyommatus species changed from local to widespread. The highest number of lycaenid species was recorded in July with a total of 40 species per month. Widespread lycaenid species were generally caught at altitudes higher than 1000 m. Altitudinal distribution and phenology of lycaenid species as well as their new host plants found are discussed.