Background <p>Life participation is a priority outcome for children and families living with chronic kidney disease (CKD). This study aimed to assess the construct validity of the PRO-Kid-LP, a novel three-item tool measuring CKD’s impact on children’s life participation.</p> Methods <p>Participants were children aged 8–18&#xa0;years from Canada, with stages 3–5 CKD, who were part of the PRO-Kid validation cohort. Using 5-point adjectival scales, the PRO-Kid-LP tool measures CKD’s impact on three domains over 1&#xa0;week: (1) school participation, (2) meaningful time with family and friends, (3) participation in hobbies/recreational activities. Higher scores reflected more impact of CKD on life participation. The PedsQL™ and PRO-Kid symptom assessment tool were also completed. Construct validity was evaluated with Spearman correlations and internal consistency, with Cronbach’s alpha (<i>C</i>_α).</p> Results <p>Ninety-seven children were included, with a mean age of 14.4&#xa0;years (IQR 11, 16.6), and 62.9% (61/97) were male. Impact on life participation increased by CKD stage (<i>p</i> = 0.003). There was an inverse relationship between PRO-Kid-LP and PedsQL™ scores (<i>r</i> =  − 0.65, <i>p</i> &lt; 0.001), and a positive relationship between PRO-Kid-LP scores and CKD symptoms (PRO-Kid frequency [<i>r</i> = 0.51, <i>p</i> &lt; 0.001] and impact [<i>r</i> = 0.49, <i>p</i> &lt; 0.001] scores). PRO-Kid-LP scores were associated with the PRO-Kid “Feeling left out” item (<i>p</i> &lt; 0.001). Internal consistency was high (<i>C</i>_α = 0.81), which supports reliability.</p> Conclusions <p>This study supports the validity of the PRO-Kid-LP to quantify the impact of CKD on life participation in children with stages 3–5 CKD. The tool shows internal consistency, a positive correlation with symptom burden, and a negative correlation with quality of life.</p> Graphical abstract <p></p>