The study sought to determine the impact of the Big Five personality characteristics on aggressiveness among school children aged 12 to 16 in the Jenin governorate. The study employing the Big five-factor scale of Macri and Costa and the scale of aggressive behaviour in three areas [aggressive behaviour against oneself, aggressive behaviour against others, and aggressive behaviour against property]. The sample size in this study was 314 students. The quantitative study tool [the questionnaire] revealed the following correlation between the five major personality factors and aggression: neuroticism [+], openness [-], conscientiousness [-], extraversion [-], agreeableness [-]. The most prevalent main personality variables were conscientiousness and neuroticism. The degree of aggressiveness in the Jenin governorate was relatively low on the overall scale.