The aim of this study is to determine whether the presence of the interjection ‘um’ can distinguish between the deceptive and truthful speech of individuals who are practised in the art of impression management. A total of 50 truthful and 61 deceptive statements were extracted from the speech of celebrities participating in a televised comedy panel show where celebrity guests try to convince an opposing team of their truthfulness. Participants’ use of ‘um’ (measured as a percentage of the total word count of each statement) was analysed. The results show that, on average, ‘um’ was used almost three times as often in the speakers’ true statements compared to their false ones. A discriminant analysis revealed that the presence of ‘um’ is more effective than human judgement alone in determining veracity. These findings suggest that the presence of the filler ‘um’ in speech is useful in the identification of true versus false oral statements.