An exhaust gas purification system for an internal combustion engine is herein disclosed which comprises an exhaust system having an adsorption flow path provided with an adsorbent capable of adsorbing harmful components such as hydrocarbons in an exhaust gas, and a catalyst flow path provided with at least one catalyst for decreasing the harmful components in the exhaust gas, the exhaust gas purification system being characterized in that an outlet of the adsorption flow path is joined to the catalyst flow path at a predetermined position on the upstream side of the catalyst to form a joint portion; the exhaust gas produced at least at the time of the operation start of the internal combustion engine is divided so as to flow through both the adsorption flow path and the catalyst flow path in a predetermined ratio, so that part of harmful components such as the hydrocarbons are adsorbed by the adsorbent in the adsorption flow path; and when the adsorbed harmful components begin to desorb from the adsorbent with the temperature rise of the adsorbent, the catalyst on the downstream of the joint portion is activated.