The crystallization of L-menthol in water was investigated, with the intent of understanding the effect that liquid-liquid phase separation (LLPS) has on the properties of product crystals. First, the binary phase diagram was measured, comprising both solid-liquid and liquid-liquid equilibrium regions. Calibration for the online monitoring of solid and liquid-liquid suspension densities was performed using Raman spectroscopy, thus enabling the detection of LLPS and crystallization. Crystallization was monitored online also by Raman spectroscopy. Offline characterization was performed using differential scanning calorimetry, powder X-ray diffraction, and Karl-Fisher. Crystallization followed by LLPS led to the formation of the most stable polymorphic form, yet those solids contained solvent inclusions. The initial amount of inclusions proved to be a function of operating conditions, namely cooling rate and suspension density.