After Burebista's death, the empire he had created broke up into smaller kingdoms. From the reign of Tiberius to Domitian, Dacian activity was reduced into a defensive state. The Romans abandoned plans of mounting an invasion against Dacia. In 86 CE the Dacian king, Decebalus, successfully re-united the Dacian kingdom under his control. Domitian attempted a hasty invasion against the Dacians that ended in disaster. A second invasion brought peace between Rome and Dacia for nearly a decade, until Trajan became emperor in 98 CE. Trajan also pursued two conquests of Dacia, the first, in 101–102 CE, concluded in a Roman victory. Decebalus was forced to agree to harsh terms of peace, but did not honour them, leading to a second invasion of Dacia in 106 CE that ended the independence of the Dacian kingdom.

After its integration into the empire, Roman Dacia saw constant administrative division. In 119, it was divided into two departments: Dacia Superior ("Upper Dacia") and Dacia Inferior ("Lower Dacia"; later named Dacia Malvensis). Between 124 and around 158, Dacia Superior was divided into two provinces, Dacia Apulensis and Dacia Porolissensis. The three provinces would later be unified in 166 and be known as Tres Daciae ("Three Dacias") due to the ongoing Marcomannic Wars. New mines were opened and ore extraction intensified, while agriculture, stock breeding, and commerce flourished in the province. Roman Dacia was of great importance to the military stationed throughout the Balkans and became an urban province, with about ten cities known and all of them originating from old military camps. Eight of these held the highest rank of colonia. Ulpia Traiana Sarmizegetusa was the financial, religious, and legislative center and where the imperial procurator (finance officer) had his seat, while Apulum was Roman Dacia's military center.

From its creation, Roman Dacia suffered great political and military threats. The Free Dacians, allied with the Sarmatians, made constant raids in the province. These were followed by the Carpi (a Dacian tribe) and the newly arrived Germanic tribes (Goths, Taifali, Heruli, and Bastarnae) allied with them. All this made the province difficult for the Roman emperors to maintain, already being virtually lost during the reign of Gallienus (253–268). Aurelian (270–275) would formally relinquish Roman Dacia in 271 or 275 CE. He evacuated his troops and civilian administration from Dacia, and founded Dacia Aureliana with its capital at Serdica in Lower Moesia. The Romanized population still left was abandoned, and its fate after the Roman withdrawal is controversial. According to one theory, the Latin spoken in Dacia, mostly in modern Romania, became the Romanian language, making the Romanians descendants of the Daco-Romans (the Romanized population of Dacia). The opposing theory states that the origin of the Romanians actually lies on the Balkan Peninsula.