Abstrak Penelitian ini mengkaji penerapan asas nemo judex in causa sua terkait dengan Putusan Mahkamah Konstitusi Nomor 90/PUU-XXI/2023 tentang batasan usia calon presiden dan wakil presiden. Menggunakan metode penelitian yuridis normatif, penelitian ini membahas kontroversi putusan tersebut yang dinilai menguntungkan Gibran Rakabuming Raka, anak Presiden sekaligus keponakan Ketua Majelis Hakim MK, Anwar Usman. Putusan MK ini dianggap menyalahi asas nemo judex in causa sua yang melarang hakim mengadili perkara yang menyangkut kepentingan pribadinya atau keluarganya. Hasil penelitian menunjukkan bahwa MK telah melanggar asas tersebut sehingga putusannya dinilai batal demi hukum. Penelitian ini menyimpulkan bahwa untuk menjaga independensi dan imparsialitas peradilan, penerapan asas nemo judex in causa sua harus dipertegas dalam regulasi dan pelaksanaannya di lingkungan MK. Kata Kunci; Asas Nemo Judex In Causa Sua, Mahkamah Konstitusi. Abstract This research examines the application of the nemo judex in causa sua principle in relation to the Constitutional Court Decision Number 90/PUU-XXI/2023 concerning age limits for presidential and vice presidential candidates. Using normative juridical research methods, this research discusses the controversy over the decision which is considered to benefit Gibran Rakabuming Raka, the President's son and nephew of the Chief Justice of the Constitutional Court, Anwar Usman. The Constitutional Court's decision is considered to violate the principle of nemo judex in causa sua which prohibits judges from hearing cases involving their personal or family interests. The research results showed that the Constitutional Court had violated this principle so that its decision was considered null and void. This research concludes that to maintain the independence and impartiality of the judiciary, the application of the principle of nemo judex in causa sua must be emphasized in regulations and implementation within the Constitutional Court. Keywords; Principle of Nemo Judex In Causa Sua, Constitutional Court.