Andreas enjoyed a stellar career as a student in Basel, Freiburg im Breisgau, and Berlin, completing his studies in 1887 in Freiburg with the doctoral thesis "Beitrag zum Consonantismus der Mundart von Baselstadt" ("A Contribution on Consonantism in the Dialect of Basel").

He focused on research into Old Norse literature, especially the Poetic Edda and Íslendingasögur, translating many works into German and traveling twice to Iceland.

Besides ancient Germanic and Nordic culture, Heusler was noted for his love of music (he played the violin); around 1889 he switched from a strongly held Christianity to being a confirmed atheist.

[2] A good insight into his thoughts is offered by the four hundred letters to Wilhelm Ranisch which he wrote in the period 1890–1940.

Andreas Heusler was among the most influential figures in early Germanic studies in the first half of the twentieth century, and much of his work still resonates today, including the more questionable field propositions concerning "German-dom" and their reflection in early philological work.