Nowadays, education is an unseperatble part of indivudials' career succesfull. Vocational schools play an important role to increasing the chance to individuals get a future bright of their career life. The paper shows an effort to explain the relationship between internal locus of control with vocational maturity among vocational students in Medan, Indonesia. A total of 115 respondents were selected from 460 of total population in a public vocational school. Data were collected through a survey among the participants manually and the research employs the Pearson Correlation to analyze the data and test the hypothesis. Result pointed out that correlation coefficient r xy = 0,562 with p value = 0.000 (p <0,050). In summary, the internal locus of control as the independent variable has a relationship with the vocational maturity.