Neurological soft signs (NSSs), minor neurological abnormalities, have been implicated as risk factors for poor cognitive performance in small-scale studies. Here we investigate the associations between NSSs and multiple domains of cognitive performance in a large, population-based cohort and evaluate sex differences in these associations. We analyzed data from 35,710 seven-year-old children in the Collaborative Perinatal Project to study the association between the number of NSSs and cognitive test scores using multiple linear regression models adjusting for risk factors for brain injury and aberrant neurodevelopment. NSSs were associated with lower scores on all domains of cognitive performance. Each additional soft sign was associated with lower full-scale IQ (b = -4.83, 95% CI [-5.06, -4.60]), performance IQ (b = -4.28, 95% CI [-4.54, -4.02]), and verbal IQ scores (b = -4.53, 95% CI [-4.76, -4.30]), as well as arithmetic (b = -4.06, 95% CI [-4.26, -3.85]), spelling (b = -3.53, 95% CI [-3.75, -3.30]), and reading (b = -4.00, 95% CI [-4.26, -3.75]) scores on the Wide Range Achievement Test (WRAT). Only one sex difference was observed: The association between NSS and the WRAT spelling test was somewhat stronger in girls (b = -4.01, 95% CI [-4.26, -3.36]) than in boys (b = -3.53, 95% CI [-3.75, -3.30]). There is an association between NSSs and poor cognitive performance that is not attributable to established risk factors for brain injury and aberrant neurodevelopment. Further research is needed to investigate the mechanisms underlying this association and to determine if interventions targeting NSS in children might have beneficial effects on neurocognitive development.