The bring-your-own-device policy (BYOD) in schools has recently attracted considerable research interest. BYOD allows students to learn subjects like mathematics using personal mobile devices. Accordingly, BYOD can increase students' desire to learn mathematics in school. In the study we report on here, we assessed 9th grade students' (n = 500) behavioural intentions to learn mathematics using personal mobile devices in school. Data were collected from 12 urban and rural Namibian public schools through a paper survey. Drawing on the theory of reasoned action with an added facilitating condition component, we predicted students' behavioural intentions to learn mathematics based on BYOD. The descriptive results show that most students own personal mobile devices and are eager to use them as part of their learning in school. Principal component and confirmatory factor analyses validated the 4-component model. The results indicate satisfactory construct validity. Structural equation modelling was used to examine the influence of the factors on the students' behavioural intentions. The structural equation modelling results show that the theory of reasoned action and facilitating condition factors predicted students' behavioural intentions toward BYOD for mathematics learning in school. The findings suggest that educational policymakers should amend existing policies to allow students to learn mathematics using personal mobile devices in school.