Electron field emission from an array of micro-patterned monolithic diamond tips with varying sp2 content has been systematically investigated. The experimental results show that the field emission characteristics can be improved and the turn-on electric field can be reduced more than 50% by increasing sp2 content. Two hypotheses are proposed as an explanation of the effect of sp2 content on the field emission characteristics of diamond tips: the lowering of the work function due to defect-induced band generated bysp2 content in the diamond lattice and an increase in the field enhancement factor due to embedded sp2–diamond–sp2 cascaded microstructures.