Watermelon ranks fifth in Malaysian fruit production after coconut, durian, banana and pineapple. Its export value has increased significantly at 6.2%, from 60 thousand MT (2018) to 64 thousand MT. Losses happen throughout the supply chain, especially during the production and logistic process. The watermelon supply chain involves one- or two- tier supply chain, which comprises movement from producers, wholesalers, retailers and final users. A preliminary survey had been conducted to estimate the postharvest losses percentage along the supply chain. The total postharvest loss for watermelon in Malaysia was high at 33%, with losses at the collection centre accumulating the highest percentage (56%). This high loss needs to be addressed as it will affect the farmers’ income and lead to an increase in food waste in the agriculture sector. A study on sanitation treatment to reduce fungal infection and extend the shelf life of watermelon was conducted. Sanitation treatments consisted of dipping the watermelon fruit in water treated with 250 ppm sodium hypochlorite for 30 seconds (Treatment 1) and spraying the peduncle with 250 ppm propiconazole fungicide (Treatment 2). Unsanitized fruit was set as control (Treatment 3). Results showed that sanitized watermelon samples (dipped in sodium hypochlorite or sprayed with propiconazole) rated acceptable until four weeks of storage at the ambient temperature of 27°C. Unsanitized fruit was infected with mould and thus rated as poor. Biochemical properties were not affected by sanitation treatment. In conclusion, sanitation using 250 ppm sodium hypochlorite or 250 ppm propiconazole helps slow down the fungal infection and extends the shelf life of watermelon fruit up to four weeks. This sanitation treatment is recommended to be included in the watermelon postharvest handling procedure to maintain good quality, reduce losses and expand the market for domestic and export.