The Pr:YAG thermographic phosphor was employed to perform precise single-shot 15-kHz surface temperature measurements of a thermal barrier-coated 4140 steel substrate located in the cylinder head of an optically-accessible engine for two homogeneous-charge compression-ignition (HCCI) operating conditions. The ability of lifetime-based phosphor thermometry to track the highly-transient temperature swings expected in thermal barrier-coated engines was evaluated in terms of both measurement precision and biases. Single-shot precision over a single engine cycle was estimated to be 1.4 K (one standard deviation) based on a recently developed technique that utilizes weighted linear regression statistics. The precision predictions are in excellent agreement with direct measurements during periods where the surface temperature is relatively constant. Precision was slightly degraded for ∼15 crank-angle degrees (CAD) slightly before top dead center (TDC), due to attenuation of the signal. High background luminosity for the high-load HCCI case was observed during the main heat release, leading to interference with the phosphor signal and resulting in loss of data over a few CAD just before TDC. Heat transfer modeling indicated that the 11 μm thick phosphor coating resulted in a modest level of intrusiveness, with maximum expected temperature differences across the phosphor layer of ∼10 K at the highest temperatures for the high load case. The results indicate that high-speed phosphor thermometry with the Pr:YAG phosphor is a promising diagnostic to quantitatively evaluate the performance of new thermally insulating materials in transient environments.