High performance flexible field emitters made of aligned pyramidal shaped conducting ultrananocrystalline diamond (C-UNCD) microtips on polynorbornene substrates is demonstrated. Flexible C-UNCD pyramidal microtips show a low turn-on field of 1.80 V/μm with a field enhancement factor of 4580 and a high emission current density of 5.8 mA/cm2 (at an applied field of 4.20 V/μm) with life-time stability of 210 min. Such an enhancement in the field emission is due to the presence of sp 2-graphitic sheath with a nanowire-like diamond core. This high performance flexible C-UNCD field emitter is potentially useful for the fabrication of diverse, flexible electronic devices.