Flexible materials are important for the development of neural probes in recording stable signals (spikes) in vivo. Here, we present inkjet-printed, flexible neural probes for spike recording by using polymeric thin films. The neural probes were constructed from 400 nm-thick poly(D,L-lactic acid) nanofilms, inkjet-printed lines consisting of Au and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate nanoinks, and fluoropolymer layers. Microelectrodes were exposed by cutting the edge with a razor. The 6 μm-thick probes were connected to the external amplifiers by gradual increase of stiffness with thickness-dependent manner. The probe was formed into a needle shape, which recorded spikes from mouse thalamus in vivo.