Penelitian ini bertujuan untuk menganalisis pengaruh anchoring bias, illiquidity, dan trading volume activity (TVA) terhadap cumulative abnormal return (CAR) pada saham yang melakukan stock split di Bursa Efek Indonesia periode 2014–2024. Menggunakan pendekatan event study dan regresi linier berganda dengan tiga event window (CAR[-5,5], CAR[-3,3], CAR[-1,1]), analisis dilakukan terhadap 105 sampel saham dengan koreksi robust menggunakan metode Huber-White (HC1). Hasil menunjukkan bahwa anchoring bias berpengaruh negatif dan signifikan terhadap CAR pada jangka waktu CAR[-5,5] dan CAR[-3,3], namun tidak signifikan pada jangka sangat pendek CAR[-1,1]. Sementara itu, variabel illiquidity tidak menunjukkan pengaruh signifikan di semua model. Sebaliknya, TVA terbukti berpengaruh positif dan signifikan secara konsisten terhadap CAR dalam seluruh jendela waktu, menunjukkan bahwa aktivitas perdagangan yang tinggi mendorong peningkatan abnormal return pasca stock split. Temuan ini mendukung teori behavioral finance terkait bias kognitif investor serta literatur mengenai efek sinyal dari volume perdagangan. Penelitian ini diharapkan dapat menjadi referensi dalam memahami perilaku pasar terhadap aksi korporasi serta membantu manajemen dalam merancang strategi yang memperhatikan dinamika psikologis dan teknikal pasar./This study aims to examine the effect of anchoring bias, illiquidity, and trading volume activity (TVA) on cumulative abnormal return (CAR) following stock split announcements in companies listed on the Indonesia Stock Exchange during the 2014–2024 period. Using an event study approach and multiple linear regression across three event windows (CAR[-5,5], CAR[-3,3], and CAR[-1,1]), the analysis is based on 105 stock samples with robust standard error adjustments via the Huber-White (HC1) method. The results show that anchoring bias has a consistently negative and significant effect on CAR in the medium-term windows (CAR[-5,5] and CAR[-3,3]), but becomes insignificant in the very short-term window (CAR[-1,1]). Meanwhile, the illiquidity variable does not show any significant effect in all models. On the other hand, TVA is consistently positive and statistically significant across all windows, indicating that higher trading activity contributes to greater abnormal returns post-split. These findings support behavioral finance theory regarding investor cognitive biases and align with literature on the informational role of trading volume. This research provides practical insights for corporate management in designing stock split strategies and serves as a valuable reference for investors and scholars in understanding market reactions shaped by behavioral and trading dynamics.