The influence, on theory of mind development, of asking children to verbally justify their own answers to traditional tests of false belief understanding was investigated using a microgentic procedure. 18 nursery school children, (mean age 3 years 9 months) completed 6 testing sessions at 2-week intervals over a 3-month period. The unexpected transfer prediction task, deceptive box task and an unexpected transfer explanation task were administered to all children at the first phase of testing. Following which, the children were allocated, on the basis of matched pairs, to the experimental or control group. Both groups answered the same 3 false belief questions encountered in the unexpected transfer prediction and deceptive box tasks in the following 4 testing sessions. The experimental group was also asked two additional justification questions requiring an explanation of their own test question responses. The testing procedure at the final phase was identical for all participants and took the same format as at the first, with the reintroduction of the unexpected transfer explanation task. Contrary to predictions the results revealed no significant between group difference in developmental improvement of false belief scores from the initial to final testing phases (F(1, 16)=.831, p=0.375). Compared to the control group, the experimental group also failed to show a more stable developmental trajectory or increased sophistication of unexpected transfer explanation task responses at the final testing phase. Thus evidence was not found to support the claim that providing justifications facilitates the development of false belief understanding. Further analyses examined the types of justifications given and the sequence of task difficulty. Explanations for the current findings are considered in terms of methodological limitations and potential theoretical implications.