Control of waterborne gastrointestinal parasites represents a major concern to water industries worldwide. In developed countries, pathogens in drinking water supplies are normally removed by sand filtration followed by chemical disinfection. Cryptosporidium spp. are generally resistant to common disinfection techniques and alternative control strategies are being sought. In the current study, the photocatalytic inactivation of C. parvum oocysts was shown to occur in buffer solution (78.4% after 180 min) and surface water (73.7% after 180 min). Viability was assessed by dye exclusion, excystation, direct examination of oocysts and a novel gene expression assay based on lactate dehydrogenase 1 (LDH1) expression levels. Collectively, this confirmed the inactivation of oocysts and scanning electron microscopy (SEM) confirmed cleavage at the suture line of oocyst cell walls, revealing large numbers of empty (ghost) cells after exposure to photocatalytic treatment.