In 1937 he earned his doctoral degree from the University of Breslau for a dissertation written under Friedrich Wilhelm Maier on "faith" in the Gospel of John.
In the same year, he was ordained a priest by Cardinal Adolf Bertram and began pastoral work in Silesia until he was expelled from there in 1946.
He then earned his habilitation degree in New Testament Exegesis in 1947 with Das Heilsgeschehen bei der Taufe nach dem Apostel Paulus (Salvation through Baptism according to the Apostle Paul).
His habilitation advisor was Friedrich Wilhelm Maier, then at the Ludwig Maximilian University of Munich, which is where Schnackenburg was made Privatdozent in 1948.
Schnackenburg was a member of the International Theological Commission (ITC), wrote numerous books (including a commentary on the Gospel of John) and worked on the translation of the German Einheitsübersetzung of the Bible.