Several morphologically different Cu-oxide nanocrystals (cube, exposing only the (100) facets; elongated octahedron, exposing only the (111) facets; normal octahedron, exposing only the (111) facets; rounded octahedron, exposing only the (111) facets; truncated edge cube, exposing the (100), (110), and (111) facets) have been prepared. Mixed oxidation state facets were obtained, with the X-ray Photoelectron Spectroscopy revealing that both Cu^I and Cu^II are present in the samples. The % Cu^I and Cu^II vary for the different morphologies. Morphologies exposing the (111) facet showed the highest % Cu^I present, with the morphologies exposing the (100) facet showing the least amount of Cu^I. The glassy carbon electrode’s surface was modified with these Cu-oxide nanocrystals and their sensing performance for glucose detection was investigated. The limits of detection (LOD) observed for all the Cu-oxide nanocrystal electrodes were < 2 μM. Electrodes modified with Cu-oxide nanocrystals exposing the (111) facets and having more Cu^I present in the sample resulted in better glucose detection limits.