On the territory of the modern city were found the tombs of the ancient age and the traces of an early medieval settlement (the Xth century). Karaömer was founded in 1715 in the Ottoman Empire. Following the Russo-Turkish War of 1877-1878, the settlement became a Romanian territory, being colonized with Romanians from Oltenia, Muntenia and Moldova due to the low population. During the First World War, Caraomer was the scene of heavy fighting between the Entente forces (the Kingdom of Romania and the Russian Empire) and those of the Central Powers (the German Empire, Bulgaria and the Ottoman Empire). The Romanian and Russian troops, on the line Oltina-Negru Voda-Mangalia, were defeated and retreated to the north. Between May 1918 and November 1919, the village of Caraomer was under Bulgarian administration, following the Treaty of Bucharest of 1918.
During the Second World War, the village of Negru Voda was the scene of another battle. On August 25, 1944, a company from the 2nd Border Guard Regiment stopped the advance of a German motorized column of an anti-aircraft artillery unit that was withdrawing from Cobadin. Before 1968, Negru Voda was a district residence, and later it was a commune center. In 1989, Negru Voda was declared an agro-industrial town.
After the Russo-Turc War of 1877-1878, the Caraomer commune had the following villages in 1880: Caraomer (53 Tatar families), Alibeichoi (8 families of cerchezi, abolished), Canlicicur (95 colonial Tartar families, abolished before 1989), Dauluchioi (19 Turkish families), Ghiuvenlia (45 Turkish families), Cherchezchioi (18 Turkish families), Derechioi (11 families of Tatars, abolished), Docuzaci (8 Turkish families), Mamuzlia 3 families of Turks), Calfachioi (12 Turkish families). The Vâlcele Valley (then called Valala) belonged to Cotu Văii commune (the historical name: Chiragi) and had only 2 Turkish families. Many Muslim families have disappeared or emigrated in the aftermath of the war, the area being later colonized by Romanians. In 1902, Caraomer had 12 Turks and 239 Tartars, Dauluchioi had 89 Turks, and Valala had 37 Turks. The Muslim community in the city has a glazed structure built around 1867.
In 1930, the population had about 4,800 people, of which about 3850 were Romanians, 600 Turks and Tatars, 100 Bulgarians and 50 people were of Russian, Rroma, Armenian, Gagauz and German origin. As a result of the 2002 census, 5552 people lived in Negru Voda, of which 5404 were Romanians, 73 were Turks, and 63 were Tatars. Approximately 4500 people lived in the city itself, and the rest lived in the two villages of Darabani and Vâlcelele, which belong to the city. The village of Grăniceru, although still listed in the localities in Romania, is in fact decommissioned and depopulated.