Moisture is found to be a major cause of LED lumen degradation along with various other factors. In this work, a method is proposed to prevent moisture from penetrating into the LED’s internal structure by having diamond like carbon (DLC) films coated on the LED’s encapsulant as a moisture barrier sheet via RF sputtering system at room temperature. However, we found that the DLC coating is not suitable for this role as it underwent structural changes with time that lower its moisture resistance ability. The LED encapsulant expansion is found be the reason for the DLC’s structural changes. Consequently, higher lumen degradation is observed for LEDs coated with DLC coating as compared to its non- DLC counterpart.