Introduction Carers of peritoneal dialysis patients may suffer from burden, the characteristics of which differ from burden due to dementia, cancer or other dependent conditions. Aims To ascertain the reliability and validity of the Peritoneal Dialysis Carer Burden Questionnaire (PDCBQ), previously created, and to design the burden scale. Methods Observational, multicentre study of carers and patients on peritoneal dialysis for more than 3 months. Sociodemographic characteristics of patients and carers, patient dependency, perceived health (SF-36) and carer burden (Zarit scale) were recorded, as well as PDCBQ via 3 scales: dependence, subjective burden and objective burden. Results One hundred seven patients and their carers from 8 hospitals were evaluable. Carers were mainly women (83.2%), aged 57.50 ± 14.69 years, and 36.4% worked out of the home. The internal consistency of the Zarit scale and the PDCBQ were high (Cronbach's α between 0.808 and 0.901). Significant correlation was found between the Zarit scale and PDCBQ (r = 0.683). The concordance analysis between three degrees of Zarit scale and PDCBQ tertiles was good or acceptable (Kendall τ-b: 0.570, p < 0.001). The exploratory factor analysis of the main factors revealed 3 factors, which were successfully correlated with the design of the PDCBQ. A new carer burden scale was designed. Conclusions The study shows good reliability with high internal consistency of the PDCBQ. Factorial analysis shows good construct and good correlation, and acceptable concordance with the Zarit burden scale confirmed criterion validity. The questionnaire is suitable to be applied in clinical practice.