Bleached NBSK (Northern Bleached Softwood Kraft) pulp was fractionated using a pilot pressure screen. Then the fractionated fibres were characterized using a Fibre Quality Analyzer (FQA) and Scanning Electron Microscope (SEM). It was found that the mean fibre length and width significantly decreased after fractionation. Aspect ratio (length divided by width) of the fractionated fibres was lower than NBSK fibres. The SEM analysis indicated that the diameter of the NBSK fibres was in the range of 100 to 200 mm, while the fractionated fibre diameters were found to be 10 to 40 nm. The fibre length of the fractions varied from a few hundred nanometres to a few micrometres. The fractionated fibres were incorporated into sodium alginate-based biodegradable films during solution casting. It was found that the fractionated fibres significantly improved the mechanical properties of the sodium alginate films.