Although personality traits can influence information-seeking behaviour (ISB), research on this relationship has received inadequate attention from researchers particularly at the secondary-school level. This study identified which of the individual Big Five Personality Traits (BFPT) had a significant effect on ISB and whether BFPT combined with either gender, programs of study, or achievement had an effect on ISB. Data collection involved a self-report survey with Thai secondary-school students (n=3400). Data analysis involved multiple regression, correlation, and two-way Anova. Results showed that of the five BFPT traits, Openness to experience followed by Conscientiousness had a significant effect on ISB. High levels of Extraversion, Agreeableness, Conscientiousness and Openness predicted higher achievement and ISB. Conscientiousness, Openness to experience, Extraversion, and Agreeableness were positively correlated with ISB. Neuroticism negatively correlated with ISB. Extraversion, Conscientiousness, Openness to experience, positively correlated with academic achievement. Females with any of the five BFPT had higher ISB mean scores than males. Students in Mathematics-Science program with any BFPT had higher ISB mean scores than those in Language Arts-Social Studies program.