The sintering behavior of green pellets obtained from nanostructured Ce0.8Gd0.2O1.9 submillimetric microspheres is studied in the present paper. Corresponding shrinkage rate curve shows a two-step densification in dynamic conditions, with the presence of two successive extrema, at 1200 K and 1500 K. To fully understand this non-common densification behavior, an iterative study was performed. Multiple characterizations point out multiscale organization of the matter with temperature giving rise to differential sintering stages of two different particle size classes. Concerning 1200 K-first shrinkage rate maximum, it corresponds to the densification of nanometric aggregates of crystallites into submicrometric pre-sintered aggregates, resulting in a specific porous microstructure with residual open porosity. As-generated porosity combined with submicron size of pre-sintered aggregates thus prevent from a homogeneous sintering illustrated by a single maximum shrinkage rate. Finally, the second maximum shrinkage rate at 1500 K can then be associated to optimal temperature for submicrometric particles sintering.