The aim of this study was to prepare complex films based on chitosan and ulvan through crosslinking and analyze their bioactivities. The ulvan extracted from Ulva lactuca was composed of uronic acid and sulfated rhamnose as the main monosaccharides in which it had a sulfate content of 16.25 ± 1.19 wt%. During preparation, ionic crosslinking occurred between chitosan and ulvan and enhanced by adding tripolyphosphate and glycerol, in which the tensile strength was increased from 1.09 to 2.67 MPa. Compared to chitosan-based film, the complex films had higher swelling ratio and water vapor transmission rate. The complex films showed antioxidant and whitening activities mainly due to the ulvan. A sustained ulvan release (40–65% for 12-h releasing) from these films was observed. Especially, addition of chlorophyll to films increased the ulvan release to 64.8% and enhanced their bioactivities, showing a synergism effect. They were biocompatible to normal cells but toxic to melanoma cancer cell, presenting cell selectivity which was related to the reactive oxygen species generation. Briefly, the crosslinked complex films based on chitosan and ulvan with suitable physicochemical properties and improved antioxidant and whitening ability could have a great potential to be used as a new biomaterial in the future.