Nanocellulose has crystalline domains and can be extracted from renewable cellulosic sources. They are commonly used to increase mechanical properties of the biodegradable polymer films. This paper reports a new nanofibrillar cellulose (NFC) isolated from pineapple leaf fiber to be used as a filler in chitosan matrix to yield nanocomposite films. For preparing the composite, the NFC was added to chitosan solution at various concentrations (1 %, 3 %, 5 %, 7 % and 10 % w/w dry basis of the chitosan) and then to form a film, the solution was casted. Mechanical properties of the composite films, such as water vapor transmission rate, crystallinity, and morphology were investigated. The XRD result shows that the addition of nanocellulose fiber was effective in increasing the crystallinity and also increase the tensile strength of the composite films. The incorporation of the NFC in chitosan matrix also improves the water vapour barrier. These results indicate that the addition of nanofibrillar cellulose (NFC) isolated from pineapple leaf fiber can improve mechanical properties of the chitosan film and the resulted composite film is potentially used for a biodegradable plastic packaging application.