More than a hundred thousand people crisscross South Africa's international borders annually. Public opinion on this cross-border migration is decidedly hostile. According to a 2013 opinion poll, more than three-fifths of the adult population would favour closing the border. Can civic and ethnic identifications with the nation explain this opposition to immigration? Using data from the 12th (2013) round of the cross-sectional South African Social Attitudes Survey (N5 2,739) this paper was able to investigate individual attitudes towards border control. This paper investigates different dimensions of national identity. The results revealed that ethnic national attachment was an important determinant of attitudes towards border control. Such attitudes were also associated with attitudes towards immigrant assimilation and the effect of nationalism on society. For those aiming to ameliorate public sentiment on border control, this study provides a test of multiple determinants of public opinion on the issue, examining the comparative strength of each.