Purpose To assess associations between different types of electronic devices, myopic refraction and ocular biometric parameters in children aged 6–14 years in urban areas of Tianjin, China. Methods A school‐based, cross‐sectional study was performed on 566 children (302 boys and 264 girls). The children underwent a comprehensive eye examination, including cycloplegic autorefraction and ocular biometry. The children's parents completed a detailed questionnaire that included each child's demographics, the use of electronic devices and other related risk factors. Results Myopia was not associated with time spent using various electronic devices. However, the mean spherical equivalent refraction (SER) decreased by 0.28 D (p = 0.042) and 0.33 D (p = 0.018) for each 1‐h increase in the time spent using smart phones and computers, respectively. In the multiple linear regression analyses of factors associated with the SER, the standardised coefficient B for time spent reading and writing was approximately four to five times larger than the standardised coefficient for time spent using smart phones or computers. Time spent using tablets and watching television was not significantly associated with the SER. A longer axial length (AL) was associated with more time spent using smart phones (B = 0.23, p = 0.006) and computers (B = 0.26, p = 0.002) but not using tablets (p = 0.45) and watching television (p = 0.45). No significant association was found between other ocular biometric parameters and time spent using various electronic devices. Conclusions On average, a more myopic SER and longer AL were both associated with more time spent using smart phones and computers, but not with time spent using tablets and watching television. The magnitude of the association between SER and time spent reading and writing was a substantially larger than that for smart phone or computer use. Different types of electronic devices had differing levels of association with myopic refraction.