Little research has been published on the variables associated with sun protection behaviour in preschoolers. We aimed to define variables associated with sun protection behaviour of a sample of Spanish preschoolers. A cross-sectional observational study was conducted in two stages: 1) the design and validation of the measurement instrument, and 2) its application in a final sample of 100 (60 valid questionnaires) children for bivariate and multivariate binary logistic regression analyses of the data. The sun protection behaviour of the children was most strongly associated with: parental sun protection behaviour, absence or low frequency of sunburn in parents and children, and lower parental perception of obstacles to sun protection. Other significant factors were lower phototype, younger age, shorter sun exposure times and awareness of the sun as a risk factor. The role of social communication programmes, dermatologists and other agents providing information or sun protection advice was contradictory and associated with lower sun protection in some cases. Parental sun protection, absence or lower frequency of sunburns in parents and children, lower phototype of children, knowledge about sun exposure as a risk factor, younger age and lower parental perception of obstacles to their children's sun protection were significantly associated with the sun protection of the children.