Thermochromic liquid crystals (TLCs) are used to explore the temperature transients during thermal cycling for microchip-based polymerase chain reaction (PCR). By analyzing the reflected spectra of the TLCs over time, temperature vs. time trajectories were extracted and overshoots/undershoots were estimated. To our knowledge, this is the first report of TLC-based dynamic temperature measurements in a microfluidic device for all PCR temperature stages.