This work evaluates how chemical characteristics, such as polarity and aromaticity, can affect asphaltene aggregation. The asphaltene fraction was extracted from two different crude oils by precipitation in n-heptane, and these extracted asphaltenes were named A and B. Based on infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses, we found that asphaltenes B present greater aromaticity. According to X-ray photoelectron spectroscopy (XPS), asphaltene B showed higher heteroatom content. Model systems based on toluene/n-heptane/asphaltene (0.05 g/L) were prepared to evaluate the aggregation/precipitation of asphaltenes. Dynamic light scattering (DLS) analysis of aggregation kinetics revealed that aromatic asphaltenes with higher heteroatom content tend to form larger aggregates. Moreover, hydroxyl content exhibits a greater impact on aggregation compared to diffusivity. Furthermore, once the aggregates reach a critical size, the suspension stability is reduced, and the aggregates sediment. The atomic force microscopy (AFM) and DLS results revealed a wide range of particle size distribution. The larger clusters likely consisted of smaller aggregates that adhered together. Still, we highlight that the sizes of these aggregates determined by AFM are not directly comparable to the measurements obtained from DLS. The drying of the samples for the AFM measurements probably affects the asphaltene aggregation process. For this reason, the results obtained from the AFM and DLS techniques are not comparable.