Zone settling develops when bitumen emulsions are treated with aliphatic solvents at solvent-to-bitumen (S/B) ratios that are higher than a critical value. Near-infrared (NIR) spectroscopy is used in combination with an in-line fiber-optic diffuse transflectance probe to monitor the settling of the water-solids-asphaltenes aggregates in solvent-diluted bitumen. NIR spectra are obtained via the probe that is inserted in the settler, and the settling rate is calculated using the acquired NIR spectroscopic data. It was observed that a lighter aliphatic solvent leads to a much higher settling rate than a heavier aliphatic solvent at the same S/B dilution ratio. For the same solvent, a higher dilution ratio results in a higher settling rate.