Otto (Otto I. of Bamberg) was born about 1060 into a noble family in Mistelbach, Swabia. Serving initially in the household of Duke Wladislaw of Polonia, he entered the service of Emperor Henry III in 1090 and was appointed Chancellor of the Holy Roman Empire in 1101. In 1102, the emperor appointed and invested him as bishop of Bamberg in Franconia (now Bavaria), and Otto became one of the leading princes of medieaval Germany. During his tenure as Prince-Bishop, Bamberg rose to great prominence, while Otto achieved fame as missionary and as diplomat and politician, notably during the dispute between Emperor Henry IV and the papacy during which he remained loyal to the emperor. 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 successfully negotiated a peace which was signed in 1122 at Worms.

As bishop, Otto led a model, simple and frugal life, but did much to improve his ecceliastic and worldly realms. He rebuilt and completed the Bamberg cathedral after it had been destroyed by fire in 1081, improved the cathedral school, established numerous monestaries and built a number of churches throughout his realm and in Pommerania, and greatly expanded the town of Bamberg.

Among his great accomplishments was his peaceful and successful missionary work among the Pomeranians, after several previous forcible attempts by Poles and Italians to convert Pomerania to Christianity had failed. Otto became the papal legate, converted a large number of Pomeranians, notably in the towns of Pyritz, Kammin, Stettin and Julin, and established eleven churches, and became known as the "Apostle of Pomerania". After he returned to Bamberg in 1125, some heathen customs began to reassert themselves, and Otto journeyed once more to Pomerania in 1128. In the Diet of Usedom, Pomerania, he succeeded to convert all the nobles, converted further communities, and sent priests from Bamberg to serve in Pomerania. His intent to consecrate a bishop for Pomerania was thwarted by the bishops of Magdeburg and Gnesen who claimed metropolitan rights over Pomerania. Only after his 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 died on June 30, 1139, was buried in the monastery of Saint Michael in Bamberg, and was canonized in 1189 by Pope Clement III.

The area of western Prussia around Gdańsk (German: Danzig) was Christianized via Pomerania as well, and the monestary of Oliwa at Gdańsk was established at that time, while eastern Prussia was Christianized later via Riga by the Teutonic Knights.