The deterioration of water quality by pollutants is a major health issue. Actual remediation methods are limited, and, as a consequence, there is a need for new remediation technologies. In particular, nanomaterials of unique properties have been recently developed for remediation. Here, we review mechanisms and applications of carbon-based nanomaterials for the adsorption and photocatalytic removal of organic and inorganic pollutants in wastewaters. Nanomaterials allow enhanced adsorption due to strong interactions between pollutants and adsorption sites. In photocatalysis, enhanced efficiency is attributed to the improved light harvesting and reduced recombination of photo-induced electrons and holes.