SO3-H functionalized ionic liquid was prepared using 1-vinyl imidazole and 1,4 -butanesultone as source materials and then supported on mesoporous silica material (SBA-15). This supported ionic liquid catalyst was characterized using XRD, SEM, FT-IR, solid state NMR, TGA. Their catalytic activity in Tert-butylation of p-cresol with tert-butyl alcohol (TBA) was investigated in a batch autoclave. The effects of reaction time, reaction temperature, catalyst amount and reactant mole ratio on the conversion of p-cresol and 2-tert-butyl-p-cresol (TBC) and 2, 6-di-tert-butyl-p- cresol (DTBC) selectivities were investigated. Lower alcohol to p-cresol mole ratios, lower catalyst loading at 110°C gave a 65% maximum conversion of p-cresol. The recoverability and recyclability of the catalyst was also investigated. The catalyst could be completely recovered and its activity was found to be almost completely retained even after 5 recycles. The experimental data was found to satisfy a second order rate equation. The activation energy was calculated to be 5.2 kcal/mol.