<![CDATA[Abstract. This study aims to examine the forms of banks' legal liability concerning customer transactions allegedly involved in illegal cryptocurrency investments and to analyze the implementation of the Know Your Customer’s Customer (KYCC) principle by banks in preventing customer transactions from being associated with illegal crypto asset investments. This research employs a normative legal research method using both statutory and conceptual approaches. The legal sources consist of primary legal materials, including regulations governing the banking sector, anti-money laundering, and crypto asset trading, as well as secondary legal materials comprising books, scholarly journals, and other relevant legal literature. The data were analyzed qualitatively through the interpretation and harmonization of legal provisions related to banks' legal liability and the implementation of customer due diligence principles. The findings indicate that legal liability for customer transactions involving illegal cryptocurrency investments rests with the party responsible for conducting the unlawful activities. Banks are obligated to protect customers and prevent the misuse of the banking system. Weak implementation of the Know Your Customer (KYC) principle reflects deficiencies in banks' internal control systems, while the application of the KYCC principle can strengthen transaction monitoring and risk mitigation. Strengthening both KYC and KYCC is essential to maintaining the integrity and stability of the banking system. The implementation of KYC by Bank BCA and Bank Mandiri has not yet been fully optimized, as suspicious transaction patterns should be identified and monitored in accordance with Financial Services Authority Regulation (POJK) Number 8 of 2023. Abstrak. Penelitian ini bertujuan untuk mengetahui bentuk tanggung jawab hukum bank terkait dengan transaksi nasabah yang diduga terlibat dalam investasi kripto ilegal dan juga untuk menganalisis penerapan prinsip Know Your Customer’s Customer (KYCC) oleh bank guna mencegah keterlibatan transaksi nasabah dalam investasi aset kripto yang ilegal. Penelitian ini menerapkan metode penelitian hukum normatif dengan menggunakan pendekatan perundang-undangan dan pendekatan konseptual. Sumber hukum yang digunakan mencakup bahan hukum primer berupa regulasi yang mengatur tentang sektor perbankan, pencegahan pencucian uang, dan perdagangan aset kripto, serta bahan hukum sekunder yang terdiri dari buku, jurnal penelitian, dan literatur hukum yang berkaitan. Analisis dilaksanakan secara kualitatif lewat penafsiran dan sinkronisasi berbagai peraturan hukum yang relevan dengan tanggung jawab bank dan penerapan prinsip pengenalan nasabah. Temuan penelitian menunjukkan bahwa bentuk pertanggungjawaban hukum bank terhadap transaksi nasabah terkait investasi kripto ilegal menyatakan bahwa kerugian ditanggung oleh pihak yang melakukan. Bank harus melindungi nasabah dan mencegah penyalahgunaan sistem. Kegagalan KYC menunjukkan kelemahan kontrol internal bank. Penerapan prinsip KYCC dapat memperkuat pengawasan. Penguatan KYC dan KYCC penting untuk menjaga sistem perbankan. Penerapan KYC oleh Bank BCA dan Bank Mandiri belum optimal. Pola transaksi mencurigakan harus terdeteksi sesuai dengan POJK Nomor 8 Tahun 2023. ]]>
