Background: Prisoners with intellectual disabilities are known to be disadvantaged in prisons and to be more susceptible to bullying, segregation, depression and anxiety than other prisoners. Method: In this study, nearly 3000 new prisoners entering three English prisons were offered screening for intellectual disabilities, using the LDSQ. Results: On average, 75% of all new prisoners entering prison were offered screening, and only 14% refused screening. Overall, just less than 7% were screened positive on the LDSQ and prisons made some reasonable adjustments as a result. Conclusions: It is argued that it is feasible to screen for intellectual disabilities in prisons and, given the inequalities to which prisoners with intellectual disabilities are subject in prison, it is time for such screening to be rolled out to all prisons.