At preschool age, motor skills and cognitive functions are regularly examined at well-child visits. Although reliable screening depends on the stability of the assessed developmental domains, little is known about the stability of motor and cognitive performance in preschool children. The aim of the present study was to investigate how stable motor skills and cognitive functioning are in the preschool years and whether they can predict their own and respective outcome 1 year later. 509 children were examined (46.4% female; M = 3.9 years; SD = 0.6; range 3.0-6.0 years) from the Swiss Preschoolers' Health Study (SPLASHY) at baseline and 1 year later. A Latent Variable Cross-lagged Panel Model revealed that both motor skills and cognitive functioning are highly stable in the preschool age (0.65/0.67). Cross-lagged coefficients were smaller (0.37/0.22). However, as the cross-lagged paths did not differ significantly from each other, no reliable conclusions for the prediction of motor skills and cognitive functions may be drawn. We conclude that cognitive functioning and motor skills are highly stable already in the preschool years. Although small cross-lagged predictive values were found, motor skills and cognitive functions may not to be reliable predictors of their respective outcomes. Future studies should test cross-lagged predictive effects in clinical samples, where the effects might be larger.