A plastic sealing fastener includes a fixing member, a locking member defining a locking slot, a latching strip formed on the fixing member and a cover fixed on the fixing member. The locking member forms a locking portion in the locking slot. The cover defines a covering hole communicating with the locking slot, and a size of the covering hole is less than that of the locking slot. The locking portion comprises, for example, three locking teeth.