Introduction: Teachers are invited to seek answers to many questions on their professional growth path. This article aims at drawing attention to their motivational behaviour in teaching school students. According to the theory of self-determination, appropriate motivating (that is, autonomy-supportive) behaviour of teachers can respond to a child's essential psychological needs, and thus enable him or her to engage in the teaching and learning process. Therefore, the goal of this study is to examine the relationship between teachers' motivational behaviour and student engagement. Method: The sample was composed of 687 students. Two measuring instruments were used: Learning Climate Questionnaire (LCQ) (Black & Deci, 2000) and Student Engagement Scale (Lam et al., 2014). Descriptive statistics, t test, ANOVA, correlational analyses, and multiple linear regression analyses were used to analyse the data. Results: The research results suggest that teachers' motivational behaviour (students' perceived level of autonomy-supportive teaching) significantly predicts student engagement. The studied Lithuanian children are characterised by the same engagement as children from all over the world; they see the meaning of their work and focus on it. Discussion and Conclusion: The conducted research also confirms a universal trend that boys are less involved than girls, although there were no statistically significant differences in the perceived level of teachers' autonomy-supportive behaviour (for boys and girls).