Objectives Polyhandicap (PLH), defined by a combination of profound intellectual impairment and serious motor deficits, is a severe condition with complex disabilities. In France, care of the large majority of PLH individuals is managed in specialised rehabilitation centres or residential facilities, but some of PLH individuals are cared for at home. The aims of this study were to assess the self-perceived burden among informal caregivers of PLH individuals and to identify potential determinants of this burden. Design Cross-sectional study (Neuropaediatric Department, Trousseau Hospital, Paris, France). Settings PLH children were recruited from a specialised paediatric/neurological department. Participants The selection criteria of caregivers were age above 18 years and being the PLH individual's next of kin. Outcomes measures From March 2015 to December 2016, data were collected from the caregivers, including sociodemographical data, health status, psycho-behavioural data (quality of life, mood disorders and coping) and self-perceived burden. In addition, the health status of the PLH individual was collected. Relationships between the burden scores and potential determinants were tested (correlations coefficients, Mann-Whitney tests, generalised estimating equations models). Results Eighty-four children were eligible; 77 families returned their questionnaire. The informal caregivers of PLH children experienced a high level of perceived burden (scores ranged from 55 +/- 20 to 81 +/- 12). Eighty per cent of them had more than 5 hours of daily caregiving and 51% of them had to get up more than twice during the night. The main factors associated with caregiver burden were age, financial issues, health status, daily care and coping strategies. The patients' health status was not associated with caregiver burden. Conclusions Some of the caregiver burden determinants might be modifiable. These findings should help healthcare workers and health-decision makers implement specific and appropriate interventions.