A novel regioselective formylation of 1, 3, 5-triarylpyrazoline by using Vilsmeire- Haack reaction is described. The formylation only observed in N-phenyl ring in the presence of phenolic or methoxy group in 3 & 5-aryl ring. Iodine, a readily available reagent, was found to be effective in carrying out chemoselective oxidation of 1, 3, 5-triaryl pyrazolines to 1, 3, 5- triaryl pyrazoles.