The structure of the full-length multi-domain GH92 α-1,2-mannosidase fromN. novalis(NnGH92) was solved and the function of the noncatalytic domains was investigated by their sequential deletion and biochemical characterization of theNnGH92 variants. This work significantly advances the structural knowledge of multi-domain GH92 α-1,2-mannosidases and provides a better understanding for the future optimization of these enzymes for the degradation of yeast α-mannan or protein glycans.