Sviatoslav joined his brothers, Iziaslav of Kiev and Vsevolod of Pereyaslav, in forming a princely "triumvirate" that oversaw the affairs of Kievan Rus' until 1072.

The three brothers together fought against their enemies, including the nomadic Oghuz Turks, and their distant relative, Prince Vseslav of Polotsk.

[5] The Russian Primary Chronicle writes that Sviatoslav was staying "at Vladimir"[6] in Volhynia around the time his father fell seriously ill before his death.

[7] According to the historian Martin Dimnik, the chronicle's report shows that Yaroslav the Wise had, most probably in about 1040, appointed Sviatoslav to rule this important town of the Kievan Rus'.

[11] The dying grand prince also ordered that his four younger sons should "heed"[12] their eldest brother, Iziaslav, who received Kiev.

[14] Historian Martin Dimnik writes that taking into account Sviatoslav's political and military skills it "is reasonable to assume that he was one of the main motivating forces, if not the actual architect, of many of the policies adopted" by the three brothers.

[27] Vseslav, who fled from the battlefield, agreed to enter into negotiations with the "triumviri", but they treacherously captured him at a meeting at Orsha in early June.

[24][27] The Cumans, who had emerged as the dominant power of the Pontic steppes in the early 1060s, invaded the southern regions of Kievan Rus' in 1068.

[33] The townspeople of Kiev sent messages to Sviatoslav and Vsevolod, imploring them to come to their "father's city"[34] and defend it, according to the Russian Primary Chronicle.

[35] Sviatoslav and Vsevolod requested Iziaslav "not to lead the Poles in attack upon Kiev", stating that "if he intended to nurse his wrath and destroy the city, they would be properly concerned for the ancestral capital".

[35][36][33] Iziaslav partially acquiesced: he did not let his Polish allies enter the town, but his retinue slaughtered or mutilated many of his opponents in Kiev.

[37] He also attempted to punish Anthony—the founder of the Monastery of the Caves in Kiev—who had supported his enemies, but Sviatoslav gave shelter to the saintly monk in Chernigov.

[41] In short order, Sviatoslav felt a pain at the top of his head and his servant found a fingernail of the saint under his cap.

[45][50] However, before his death in May 1074 he was reconciled with the grand prince, who supported the foundation of a stone church dedicated to the Mother of God in Kiev.

[56] According to the Primary Chronicle, "in his pride", Sviatoslav "showed them his riches", displaying them "the innumerable quantity of his gold, silver and silks".

[68][69] On the other hand, German chroniclers write that his wife was Oda of Stade, a sister of Burchard, the Provost of Trier, and she gave birth to one son.

[77] Oda, the daughter of Lothair Udo I, Margrave of the Nordmark, was in some way related to Henry III, Holy Roman Emperor.