Taking into account the three key features of scaffolding, namely, contingency, fading and the transfer of responsibility, the present study investigated the role of cognitive scaffolding in speaking and its components (i.e. grammar, vocabulary, pronunciation, discourse management, interactive communication). Moreover, the possible moderating effect of learners' proficiency level was examined. Four groups of 30 female Iranian learners of English in a language school participated in this study, two of which were chosen from upper-intermediate learners, while the other two groups included learners studying at pre-intermediate levels. The results of the two-way ANCOVA tests indicated that cognitive scaffolding could foster speaking skill and its components. Besides, it was found that learners' level of proficiency did not mediate the impact of scaffolding on the studied dependent variables. Therefore, both upper-intermediate and pre-intermediate learners equally benefited from cognitive scaffolds. The study offers a number of pedagogical implications which are discussed.