Mellen Woodman Haskell was among the first American students of Felix Klein. The Harvard graduate and later professor at Berkeley stayed in Leipzig and Göttingen from autumn 1885 until summer 1889. This paper aims to shed light on his formative years up to the completion of his PhD thesis in 1890, with a focus on his time in Germany. Although few first-hand sources of Haskell remain, the information from civil, school, university and other archives provides a relatively complete picture. We also consider Haskell’s mathematical activities where this has not been done yet.