AbstractThis study investigated the effect of social skills training and values clarification counselling techniques on aggressive behaviours of senior secondary school students in Kontagora Metropolis, Niger State, Nigeria. The objective of the study was to determine the effect of social skills training and values clarification counselling techniques on aggressive behaviours (hostile, emotional, instrumental & relational) of senior secondary school students in Kontagora, Niger State, Nigeria. Pretest posttest quasi experimental design was adopted. Behaviour Rating Scale (with coefficient of 0.90) was used for the identification of the participants. The population of the study was one hundred and one (101) senior secondary school students identified with characteristics of aggression in Kontagora Metropolis, Niger State, Nigeria. A sample size of thirty (30)participants was purposively selected and fifteen (15) subjects each were assigned into two groups of social skills training and values clarification counselling. Students' Behaviour Questionnaire (with coefficient of 0.82) wasused to obtain data for both pre-test and post-test. The intervention sessions lasted for ten weeks (two sessions of 60minutes each per week)for each of the two treatment groups. Data collected were analyzed using descriptive statistics of mean, standard deviation and inferential statistics of paired sample t-test and Multivariate Analysis of Covariance. The findings revealed that social skills training counselling technique had significant effect on hostileaggressive behaviours of senior secondary school students (t=15.75, p=.000). However, social skills training counselling technique had no significant effect on emotional aggressive behavioursof senior secondary school students(t-.80, p=.435). The findings also revealed that values clarification counselling technique had a significant effect on hostile, emotional and relational aggressive behaviours of students (t=11.00, p=.000; t=6.15, p=.000 and t=7.54, p=.000) respectively. It was concluded that social skills training and values clarification counselling techniques had significant effect on aggressive behaviours of senior secondary school students in Kontagora, Niger State, Nigeria.It was recommended that school counsellors and psychologists should employ social skill training and values clarification counselling techniques in reducing aggressive behavioursofsenior secondary school students.