Background There is growing evidence confirming that youths with physical disabilities are at risk for chronic pain. Although many scales for assessing pain intensity exist, it is unclear whether they are all equally suitable for youths. The aim of this study was to address this knowledge gap by comparing the validity of the Numerical Rating Scale (NRS‐11), the Wong Baker FACES Pain Rating Scale (FACES), and a 6‐point categorical Verbal Rating Scale (VRS‐6) for assessing pain intensity among youths (aged 8–20) with physical disabilities. Methods One hundred and thirteen youths (mean age = 14.19 years; SD = 2.9) were interviewed and asked to rate their current pain intensity and recalled (in the past week) worst, least, and average pain with the NRS‐11 and the FACES. Participants were also asked to rate their average pain intensity during the past 4 weeks using a VRS‐6, and were administered measures assessing pain interference, disability and psychological functioning. Results Analyses showed that all of the pain intensity measures were associated positively with each other. Nevertheless, the NRS‐11 appeared to out‐perform both the VRS‐6 and in particular the FACES scale with respect to: (1) the associations with the validity criterion (i.e. pain interference, disability and psychological functioning) and (2) a lack of any moderating effect of age on the association between the measure and the criterion variables. Conclusions The findings support the validity of the NRS‐11 for assessing pain intensity in youths with physical disabilities between the ages of 8 and 20 years.