The current version (ver. 7.3) of the popular quantitative coronary analysis system QAngio XA (Medis Medical Imaging System BV, Leiden, the Netherlands) is widely used without evaluating the agreement between the current and older versions in relation to a change of algorithms. The purpose of this study was to assess the equivalence of averages between QAngio XA versions 7.3 and 6.0. Based on the calculated sample size, angiographic images of 100 patients who underwent percutaneous coronary intervention of a single target lesion were randomly selected from two published studies (OUCH-TL: 154 lesions; OUCH-PRO: 160 lesions). The primary endpoint was the minimum lumen diameter (MLD), and the secondary endpoints were the reference diameter (RefD) and length of the stenotic lesion (LL). Two independent analysts measured the same frame using both previous and current versions of QAngio XA. Version-order for each lesion was randomly determined per coronary locations targeted. Data were analysed by using a mixed model that includes random lesion effects and fixed rater effects and reading-order effects. A Bland–Altman plot of parameters showed no large differences between the versions. Differences in parameters were estimated by the mixed model, and the 95% confidence interval of the MLD, RefD, and LL estimates was from −0.045 to −0.0001 mm, from −0.040 to 0.006 mm, and from −1.08 to 0.46 mm, respectively, compared with the predefined non-inferiority margin of ±0.2 mm. Measurements of MLD and RefD using QAngio XA showed no major systematic differences between versions.