An approach covalently linking cardanol, a well-known renewable organic resource of the cashew industry, to PVC chains using the click reaction has been studied. Under the conditions, cardanol was covalently linked to PVC chains as a natural internal plasticizer. The modified PVC exhibited decreased glass transition temperature, excellent thermal stability and near-zero migration. We believe this approach may help researchers design and explore novel environmentally sustainable plasticizers and apply them in harsh conditions.