This work demonstrates the potential of nanoscale carbon electrode materials for improved detection of electroactive neurotransmitter dynamics in the brain. Individual multiwalled carbon nanotubes were synthesized via chemical vapor deposition, spun into yarns, and used in the fabrication of disk microelectrodes that were subsequently characterized using scanning electron and atomic force microscopies. The carbon nanotube yarn electrodes were coupled with fast-scan cyclic voltammetry and used to discriminately detect rapid neurotransmitter fluctuations in acute brain slices. The results demonstrate that the distinct structural and electronic properties of the nanotubes result in improved selectivity, sensitivity, and spatial resolution, as well as faster apparent electron transfer kinetics when compared to the conventional carbon-fiber microelectrodes typically used in vivo.