Example methods and apparatus to detect phase separation in downhole fluid sampling operations are disclosed. An example method to detect a phase separation condition of a fluid from a subterranean involves obtaining a sample of the fluid, measuring a first characteristic value of the sample, measuring a second characteristic value of the sample and comparing the first characteristic value to a first reference value associated with a single-phase condition of the fluid to generate a corresponding first comparison result. The example method then compares the second characteristic value to a second reference value associated with the single-phase condition of the fluid to generate a corresponding second comparison result and detects the phase separation condition of the fluid based on the first and second comparison results.