Cerebral palsy (CP) is a disorder of motor function often accompanied by cognitive impairment. There is a paucity of research focused on cognition in dyskinetic CP and on the potential effect of related factors. To describe the cognitive profile in dyskinetic CP and to assess its relationship with motor function and associated impairments. Fifty-two subjects with dyskinetic CP (28 males, mean age 24 y 10 mo, SD 13 y) and 52 typically-developing controls (age- and gender-matched) completed a comprehensive neuropsychological assessment. Gross Motor Function Classification System (GMFCS), Communication Function Classification System (CFCS) and epilepsy were recorded. Cognitive performance was compared between control and CP groups, also according different levels of GMFCS. The relationship between cognition, CFCS and epilepsy was examined through partial correlation coefficients, controlling for GMFCS. Dyskinetic CP participants performed worse than controls on all cognitive functions except for verbal memory. Milder cases (GMFCS I) only showed impairment in attention, visuoperception and visual memory. Participants with GMFCS II–III also showed impairment in language-related functions. Severe cases (GMFCS IV–V) showed impairment in intelligence and all specific cognitive functions but verbal memory. CFCS was associated with performance in receptive language functions. Epilepsy was related to performance in intelligence, visuospatial abilities, visual memory, grammar comprehension and learning. Cognitive performance in dyskinetic CP varies with the different levels of motor impairment, with more cognitive functions impaired as motor severity increases. This study also demonstrates the relationship between communication and epilepsy and cognitive functioning, even controlling for the effect of motor severity. •Dyskinetic CP shows a widespread lower cognitive performance than healthy controls.•Attention and visual functions are diminished in mild-to-moderate cases (GMFCS I–III).•Moderate motor impairment (GMFCS II–III) is associated with poor language measures.•Daily communication mainly correlated with receptive language functions.•Epilepsy correlated with intelligence, visual and verbal functions, and learning.