This study investigates the influence of helping and collaboration on children’s prosocial lie-telling behaviours. A total of 112 children, aged between 42 and 60 months (57 girls), participated in the study. The children in the control group were given an undesirable gift task. To see the impact of time spent with the children in the placebo control group, children completed a puzzle and then received an undesirable gift task. The children in the two different experimental groups were the recipients of helping or collaboration tasks, then their prosocial lies were measured. Results showed that the children in the experimental groups showed a significantly higher prosocial lie-telling behaviour than the control group. It was also found that there was a significant difference between the placebo group and the experimental helping group. A multinomial logistic regression analysis was conducted to clarify the predictive effects of control and experimental conditions on prosocial lie-telling behaviour. It was founded that being in the control and placebo control group significantly reduced the likelihood of prosocial lie telling behaviour. Results were discussed in light of the impact of children’s closeness with others and minimal group effects in prosocial lie-telling and cultural factors that might affect prosocial lies.