The isotropic micellar state of Pluronic P123 in the presence and absence of N-alkylpyridinium halide ionic liquids (ILs) is investigated using SANS, DLS, and 1H NMR studies. The micellar structural parameters are obtained as a function of variation in alkyl chain length, anions, and concentrations of ILs by fitting the SANS scattering data with a model composed of coreshell form factor and a hard sphere structure factor of interaction. Addition of ILs decreases the micellar core, aggregation number, and hard sphere radius of P123 micelles. From quantitative analysis, we determined the amount of solvent (D2O + IL) present inside the core and the core-shell interface along with cationic head groups. This is further supported by monitoring interaction between ILs and polymer micelle using H-1 NMR spectroscopy. The results are discussed and explained as a function of concentration of C8PyCl, alkyl chain length, and anions of N-alkylpyridinium halides.