We report a convenient and large-scale process for the preparation of CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) using stable and inexpensive olive oil to replace oleic acid as a surface treatment reagent. The obtained NCs show bright photoluminescence with absolute photoluminescent quantum yields of up to 93% and a tunable emission wavelength ranging from 409 to 689 nm. More importantly, the controllable morphology (nanocubes, nanorods, and nanospheres) of CsPbI3 NCs can be tuned by varying the reaction temperature, which may be ascribed to multiple organic ligands in olive oil that influence the growth/nucleation of the NCs. A white light-emitting diode (WLED) device was demonstrated by combining the green-emitting CsPbBr3 NCs and red-emitting K2SiF6:Mn4+ phosphors with a blue LED chip. Under operation with a 3 V forward bias voltage, the optimized WLED exhibits a high color rendering index of 85, a luminous efficiency of 46 lm/W, and a color gamut of 118% NTSC through a color filter.