This study aims to explore Ibn Taimiyah's critique of the religious philosophy of Ikhwan al-Safa and analyze the underlying reasons for his criticism. It is library research with a descriptive qualitative nature. The historical-philosophical approach is used to trace the origins of Ibn Taimiyah's and Ikhwan al-Safa's thoughts, examining the background and influences that shaped their ideas. Ibn Taimiyah's comments on Ikhwan al-Safa's thoughts are analyzed to understand his attitudes and criticisms systematically. The findings reveal that Ibn Taimiyah lived in politically turbulent times, facing challenges from Mongols, Crusaders, and internal sect divisions among Muslims. Consequently, he engaged in criticism and refutation to purify religion from what he perceived as deviant sects. The religious philosophy of Ikhwan al-Safa, criticized by Ibn Taimiyah, encompasses topics such as the religion and philosophy harmony, the emanation theory, the prophecy concept, angels, devils, and the spirit resurrection. Ibn Taimiyah's criticism of Ikhwan al-Safa aligns with other scholars' philosophy critiques. He tends to generalize Ikhwan al-Safa with other philosophers, overlooking specific differences. Ibn Taimiyah labeled them as disbelievers with a specific takfir, lacking direct arguments due to the vast time gap between them, spanning three centuries. The implication of this research is to raise awareness among Muslims about the diversity of Islamic thought, making criticism and objections a common practice. Muslims are encouraged to engage with Islamic thought and conduct scholarly rebuttals and criticisms only after thoroughly understanding the ideas they critique.