The ability to control the morphology of precipitated cerium oxalate material results in determinate evidence to its final properties. In this study, we demonstrate that surfactant-free nanostructured low-water solvents have a huge potential for controlling the morphology of a cerium oxalate powder. To this aim, an in-depth investigation of the reaction between cerium nitrate and oxalic acid is carried out, by varying both the relative concentration of the two reagents (around the stoichiometric value) and the composition of the water/propanediol/octanol ternary solvent (especially in the low-water content nanostructured domain). Thanks to the complementary of observation methods: microscopy (confocal microscopy with fluorophores and environmental SEM) and X-ray scattering (SAXS and WAXS), we evidenced the role of the solvent in the growth kinetics and directional aggregation of the precipitates—the two major factors determining the final morphology of the particles. Besides the possible confinement effect in nanodroplets, compact “dense-branching” particles, achieved in low-water content solvents, unveil the strong role of the surface forces in the aggregation mechanisms. This is consistent with the prevailing capillary forces at water/oil/solid triple points in ternary solvents. These new results confirm the high potential of nanostructured solvents for controlling the size and shape of hydrated precipitated particles.