In the last years, it has been discovered and intensely studied the non-traditional intrinsic luminescence of polyamidoamine (PAMAM) dendrimers. Nevertheless, their aging process in aqueous suspension is scarcely studied, being unknown the causes of the changes in their luminescence properties. Hence, this work aims to characterize the amine-terminated (DG4.0) and carboxylic acid-terminated (DG4.5) PAMAM dendrimers of generations 4.0 and 4.5, respectively, through the aging process at three different pH conditions, stored with or without shaking. The UV–Vis absorption, the fluorescence emission, and the dendrimer-size distribution are studied for up to 16 days. In a different way than the already published works, this work demonstrates that there is no chemical change in dendrimers through the aging process, even though changes in fluorescence emission are observed. Besides, the changes in the agglomeration patterns of dendrimers are not related to the change in the fluorescence emission through aging. Moreover, large aggregates of DG4.5 are present in water and need to be disrupted by shaking before an in vivo administration.