The energy resolution of the calibration data in CUORE-0 was determined from a fit to the 2615 keV 208Tl γ-ray line. This gives an effective FWHM value of 4.9 keV at 2615 keV;. Shown here is the calibration data near this line, integrated over all bolometers in all datasets. The solid blue line is the projection of the best model fit. In addition to (a) a double-Gaussian line shape for the main photopeak, the fit function includes (b) a multiscatter Compton continuum, (c) a ~30 keV Te X-ray escape peak, and (d) a continuum background. We extrapolate the resolution from calibration data to our background data at the 0νββ region of interest and obtain a background resolution at the Q-value of 5.1 ± 0.3 keV.