Raising Fe content has been found to deteriorate the coercivity of the cellular nanostructured Sm-Co-Fe-Cu-Zr 2:17-type permanent magnets because the insufficient 1:5H precipitates cannot occupy all the pyramidal cell boundaries. However, how the defects-aggregated cell boundaries free of 1:5H phase influence the pinning mechanism of magnetic domain walls as well as coercivity remains unknown. Through combined Lorentz and high-resolution transmission electron microscopy investigations, here we found that the magnetic domain walls of a cellular nanostructured Sm25Co44.9Fe21.5Cu5.6Zr3.0 (wt.%) magnet move from the 1:5H cell boundaries towards cell interiors, repulsed by the surrounding defects-aggregated pyramidal cell boundaries. Further investigations revealed that raising the aging temperature can effectively reduce the density of defects-aggregated cell boundaries and enhance effectively the coercivity H-cj from 5.64 to 9.24 kOe for the Fe-rich Sm25Co42.9Fe23.5Cu5.6Zr3.0 (wt.%) magnet. The comparative results suggest that the 1:5H-phase-associated attractive domain wall-pinning is more favorable for achieving large coercivity than the defects-associated repulsive domain wall-pinning. These findings add important insights into the domain wall-pinning mechanism in Sm-Co-Fe-Cu-Zr permanent magnets, which may help to achieve better magnetic performance in the Fe-rich magnets. Graphic abstract Most magnetic domain walls (e.g., dashed blue box in (a) stay at the 1:5H pyramidal cell boundaries (b), some (e.g., dashed red box in a) move towards the cell interiors repulsed by the defects-aggregated cell boundaries (DACBs) (c). [GRAPHICS] .