Investigation of the concentration dependence of the size and type C60[=C(COOH)2]3 aggregation in aqueous solutions at 25 ◦C was accomplished with the help of a dynamic light scattering method. It was determined that three types of aggregates are realized in the solutions. The average number of C60[=C(COOH)2]3 molecules in smaller aggregates and all types of aggregates were calculated. One can see that over the whole concentration range, from 0.01 to 10 g/dm3, aqueous solutions of C60[=C(COOH)2]3 are characterized by sub-micro-heterogeneous behavior (because second-type aggregates with the linear dimensions – hundreds of nm are formed in all solutions). Additionally, the most concentrated solution (C = 10 g/dm3) is characterized by micro-heterogeneous or colloid behavior (because third-type aggregates with the linear dimensions on the order of µm – are formed). In order to describe or explain such behavior, a stepwise aggregation model was invoked.