Constantine was born in Constantinople in 905, an illegitimate son of Leo VI before an uncanonical fourth marriage. To help legitimize him, his mother gave birth to him in the Purple Room of the imperial palace, hence his nickname Porphyrogennetos. He was symbolically elevated to the throne as a two-year-old child by his father and uncle on May 15, 908.
In June 913, as his uncle Alexander lay dying, he appointed a seven-man regency council for Constantine. It was headed by the Patriarch Nicholas Mystikos, the two magistroi John Eladas and Stephen, the rhaiktor
John Lazanes, the otherwise obscure Euthymius and Alexander's henchmen Basilitzes and Gabrielopoulos. Following Alexander's death, the new and shaky regime survived the attempted usurpation of Constantine Doukas, and Patriarch Nicholas Mystikos quickly assumed a dominant position among the regents.
Patriarch Nicholas was presently forced to make peace with Tsar Simeon of Bulgaria, whom he reluctantly recognized as Bulgarian emperor. Because of this unpopular concession, Patriarch Nicholas was driven out of the regency by Constantine's mother Zoe. She was no more successful with the Bulgarians, who defeated her main supporter, the general Leo Phokas, in 917. In March 919 she was replaced as regent by the admiral Romanos Lekapenos, who married his daughter Helena Lekapene to Constantine. Romanos used his position to advance to the ranks of basileopatōr in May 919, to kaisar (Caesar) in September 920, and finally to co-emperor in December 920. Thus, just short of reaching nominal majority, Constantine was eclipsed by a senior emperor.
Constantine's youth had been a sad one due to his unpleasant appearance, his taciturn nature, and his relegation to the third level of succession, behind Christopher Lekapenos, the eldest son of Romanos I Lekapenos. Nevertheless, he was a very intelligent young man with a large range of interests, and he dedicated those years to studying the court's ceremonial.
Romanos kept and maintained power until December 944, when he was deposed by his sons, the co-emperors Stephen and Constantine. Romanos spent the last years of his life in exile on the Island of Prote as a monk and died on June 15, 948. With the help of his wife, Constantine VII succeeded in removing his brothers-in-law, and on January 27, 945, Constantine VII became sole emperor at the age of 39, after a life spent in the shadow. Several months later, Constantine VII crowned his own son Romanos II co-emperor. Having never exercised executive authority, Constantine remained primarily devoted to his scholarly pursuits and relegated his authority to bureaucrats and generals, as well as to his energetic wife Helena Lekapene.
In 949 Constantine launched a new fleet of 100 ships (20 dromons, 64 chelandia, and 10 galleys) against the Arab corsairs hiding in Crete, but like his father's attempt to retake the island in 911, this attempt also failed. On the Eastern frontier things went better, even if with alternate success. In 949 the Byzantines conquered Germanicea, repeatedly defeated the enemy armies, and in 952 they crossed the upper Euphrates. But in 953 the Hamdanid amir Sayf al-Daula retook Germanicea and entered the imperial territory. The land in the east was eventually recovered by Nikephoros Phokas, who conquered Hadath, in northern Syria, in 958, and by the general John Tzimiskes, who one year later captured Samosata, in northern Mesopotamia. An Arab fleet was also destroyed by Greek fire in 957. Constantine's efforts to retake themes lost to the Arabs were the first such efforts to have any real success.
Constantine had active diplomatic relationships with foreign courts, including those of the caliph of Cordoba Abd ar-Rahman III and of Otto I, Holy Roman Emperor. In the autumn of 957 Constantine was visited by Olga of Kiev, regent of the Kievan Rus'. The reasons for this voyage have never been clarified; but she was baptised a Christian with the name Helena, and sought Christian missionaries to encourage her people to adopt Christianity. According to legends, Constantine VII fell in love with Olga, however she found the way to refuse him by tricking him to become her godfather. When she was baptized, she said it was inappropriate for a godfather to marry his goddaughter.
Constantine VII died at Constantinople in November 959 and was succeeded by his son Romanos II. It was rumored that Constantine had been poisoned by his son or his daughter-in-law Theophano.