Snijders MLH, et al. - All biopsies from patients diagnosed with C3 glomerulopathy in the period January 2005 to June 2017 in the Erasmus MC, Rotterdam were involved (n = 14) in order to examine the utility of C3d immunohistochemistry in biopsies with C3 glomerulopathy as an ancillary diagnostic tool. All 14 biopsies with C3 glomerulopathy explicated a C3d score of ≥ 2, comprising two clear-cut biopsies with C3 glomerulopathy incipiently exhibiting a trace/negative staining for C3c. In 11 biopsies, a C3d score ≥ 2 was noted in the control group. In 71% of the biopsies with C3 glomerulopathy, C4d was positive. In conclusion, in the diagnosis of C3 glomerulopathy, C3d immunohistochemistry is a valuable tool, particularly in cases in which C3c immunofluorescence reveals a trace/negative. The use of C3d additionally with C3c in cases suspicious for C3 glomerulopathy was suggested.