Objective To investigate the effect of different irrigation protocols on microhardness (MH) and flexural strength (FS) values of young and aged crown dentin. Background In addition to ageing, root canal irrigation might also affect the mechanical properties of coronal dentin walls. Materials and Methods One hundred and twenty dentin bars (2 mm x 2 mm x 8 mm) were obtained from the crowns of extracted, non-caries, human molars of young and older patients (n = 60 bars; average patient ages: 16.7 and 65.4, respectively). Subgroups were formed as follows: 2.5%NaOCl(sodium hypochlorite)+5%EDTA(ethylenediaminetetraacetic acid), 2.5%NaOCl + 15%EDTA, 2.5%NaOCl, 5%EDTA, 15%EDTA and Saline. NaOCl and saline were used for 20 minutes and EDTA solutions for 1 minute. MH values of each sample were measured before and after the irrigation protocols. The same samples were also submitted for FS analysis. The data were statistically analysed. Results Young samples had lower MH values at pre- and post-treatment compared to aged samples (P < .05). A significant decrease was observed in MH values of aged samples exposed to 2.5%NaOCl and both NaOCl + EDTA combinations (P < .05). FS values of the young saline-treated group were statistically higher than aged ones (P < .05). Both NaOCl + EDTA combinations caused a significant decrease in FS values of young samples compared to saline (P < .05). Conclusion Ageing has a significant effect on the MH and FS values of crown dentin samples. 5% EDTA solutions revealed similar results to 15%EDTA regarding MH and FS values of crown dentin in both age groups. The NaOCl + EDTA combination had a prominent effect than EDTA alone, on MH values of young-, and FS values of aged dentin samples.