In his youth he joined the household of Duke Wladislaw of Polonia. In 1090 Otto entered the service of Holy Roman Emperor Henry III and became imperial chancellor in 1101. In 1102 the emperor appointed and invested him as Bishop of Bamberg in Franconia, now Bavaria. In 1105 bishop Otto went with Henry IV to Rome. During imperial and papal quarrels Otto of Bamberg remained loyal to Henry IV and as a consequence he was suspended by a papal party at the Synod of Fritzlar in 1118. At the Congress of Würzburg in 1121 Otto engaged himself to accomplish peace, signed in 1122 at Worms.
As bishop he led a model, simple and frugal life. He completed the Bamberg cathedral and improved the cathedral school. Otto was instrumental in building castles and churches.
His greatest accomplishment was his peaceful mission among the Pomeranians. Several previous forcible attempts by Poles and Italians to convert Pomerania to Christianity had already failed. Otto of Bamberg became the legate of the pope and converted a large number of Pomeranians. Through gentle and inspiring services he converted the towns of Pyritz, Kammin, Stettin and Julin, and established eleven churches. After he had returned to Bamberg in 1125 some heathen customs began to assert themselves again. Otto journeyed once more to Pomerania in 1128 via Magdeburg and Havelberg. In the Diet of Usedom, Pomerania, he gained all the nobles and he converted further communities. He sent priests from Bamberg to Pomerania and he wished to consecrate a bishop for Pomerania, however the bishops of Magdeburg and Gnesen claimed metropolitan rights.
Only upon Otto's death in 1139 was his former companion, Adalbert, consecrated as Bishop of Julin, Pomerania (in 1140). By 1188 the diocese was moved to Hammin and made directly subject to the Holy See.
Otto of Bamberg, the Missionary and Apostle of Pomerania, continuously fulfilled his duties as bishop and prince of the empire and kept out of political turmoil. He was greatly esteemed by the Holy Roman Emperor Lothar as well.
Otto died in 1139 and was buried in the monastery of Saint Michael in Bamberg. The bishop of Würzburg delivered the funeral oration with the words of Jeremias : "The lord called thy name, a plentiful olive tree, fair, fruitful and beautiful".
Otto is reported during his lifetime to have worked many miracles and many miracles are supposed to have happened at his tomb. Pope Clement III canonized Otto in 1189 and his feast day in Pomerania is on October 1, while in Bamberg it remained in September.
The area of western Prussia around Danzig was christianized via Pomerania as well and the cloister Oliva at Danzig was established at that time, while eastern Prussia was christianized at a later time via Riga and the Teutonic Knights.