In the beginning of his Cologne period Petrus Mosellanus contributed next to the financial aid of his grandfather from Cochem to his income by offering private lessons to students. Against this background it took him until january 1512 to register at the prestigious Cologne University as a 19 year old for a study of the 7 free arts (artes liberales). Here he met his outstanding teacher Johannes Caesarius who introduced Petrus Mosellanus to de “Grammaticum” of the Greek Emanuelis Chryssolarae, the dialogues of Luciana of Samosata and the books of the poet Homerum. He met great scholars like Herman von dem Busche (earlier professor at Louvain/Belgium, Leipzig and Heidelberg in Germany) and Jacob Sobenius (coming from the Latin School of Freiberg/Saxony).
Petrus Mosellanus was mainly occupied with Greek dialectics and logic and connected these to Latin translations. He was granted the freedom of public teaching and to study and implement new teaching techniques for future students and performed this with great success. In Cologne he made the aquaintance of the Englishman Richard Croke (Crocus) whose lectures in Greek he diligently visited. His friend Caspar Borner persuaded him to move to Freiberg / Saxony together and join the Latin School of founder Raghius Aesticampianus as teachers. Continued struggles and controversies between scholastics and humanists in Cologne, which he was very much opposed to, made his decision to leave easier.
In the autumn of 1513 Petrus Mosellanus visited his grandfather in Cochem and other relatives in the moselle region and proceeded together with his friend Caspar Borner on a highly inconvenient winterjourney via Mainz, most of the time by foot, to Freiberg / Saxony. He had reached the age of 20 and had spent 3 years in Cologne.