An interrogative sentence is a sentence that the speaker puts forward to seek understanding and knowledge of a matter that is yet unknown; however, sometimes interrogative sentences are used to induce other meanings, called secondary meanings. Using this rhetorical function of language makes a literary work more eloquent, and hence, poets use this device to make the language of their work more rhetorical. The present study investigates interrogative sentences and their secondary functions in Ganjavi's Makhzan al-Asrar using a descriptive-analytical method and relying on library sources. The purpose of this study was to determine what concepts Nizami Ganjavi intended to present through the use of interrogative sentences in Makhzan al-Asrar and to what extent he was successful. The analysis of the data shows that out of the total of 225 interrogative sentences found in the book, 10 sentences are real questions and the rest are used in secondary meanings to indicate rebuke, surprise, negation, prohibition, guidance, exaggeration, etc. In general, using interrogative sentences, Nizami expressed a total of 39 themes and implicit concepts, most of which indicate rebuke and blame, and the least display pride and disappointment. In addition, the use of several secondary meanings in one sentence can also be traced in this work, which shows Nizami's high skill in using the rhetorical potentials of language.