This study used reactance theory as a starting point to explain what role a perceived undemocratic and controlling family has for adolescents' readiness to use illegal political activity. Additionally, we examined whether adolescents' readiness to use illegal political means was related to actual political behaviour, which has been lacking in research. Data came from a longitudinal sample of 424 younger (M[subscript age] = 13.44) and 296 older (M[subscript age] = 16.62) adolescents collected in a mid-sized city in Sweden. Results showed that adolescents who perceived their families as undemocratic and controlling increased in readiness to use illegal political means over time. In addition, but only for older adolescents, readiness was associated with an increase in actual political behaviour. The findings highlight the role a perceived family environment has on adolescents' development of political values and behaviours in today's democratic societies.