Aggression is characterized byvarious maladjustment behaviours with associated
negative consequences on the exhibitor andothers at different magnitudes. Though
literatures have unveiled various factors for these acts but there is a dearth of literature
on the relative and composite contributions of bio-psychosocial variables namely, gender,
personality, and parenting styles on the aggressive behaviour of pupils atlower primary
school level as this was the focus of the study in Ibadan metropolis. The study adopted
correlational research design of survey type. A total of 200 primary three pupils were
selected through a multi-stage sampling procedure. Determinants of Aggressive
Behaviours Questionnaire (α=0.81) was used to gather data which were analyzed using
descriptive and inferential statistics. Findings revealed that there is a composite
relationship among gender, personality, parenting styles and aggressive behaviours
among primary three pupils (R = .37; F (3; 196) = 10.10; p < 0.05). The relative contributions
show that parenting styles, of all the independent variable, had a significant contribution
to the aggressive behaviours of primary pupils (β = 0.35; t = 4.71; p < 0.05) among other
results. It was recommended that there is a need for awareness on parenting styles that
will not encourage aggressive behaviours among the pupils.