This study evaluated arsenic (As) removal efficiency of Japanese oak wood biochar (JOW-BC) produced at 500°C in aqueous environments. Langmuir model was the best to fit arsenite (As(III)) and arsenate (As(V)) sorption on JOW-BC, with slightly higher sorption affinity, QL, forAs(V) than As(III). The maximum As removal was 81% and 84% for As(III)- and As(V)-JOW-BC systems at pH 7 and 6, respectively, which decreased above these pH values. Surface functional moieties contributed to As sequestration by the biochar examined here. Arsenic K-edge XANES spectroscopy demonstrated complex redox transformation of As(III)/As(V) with JOW-BC. The JOW-BC led to remove As from As-contaminated drinking well water with As depletion ranging from 92–100% of total As.