AbstractThis study was undertaken to find out if teacher self-disclosure could positively effect English as
a Second Language (ESL) undergraduate students' writing performance in argumentative essays. Using
the mixed-methods intervention design. both quantitative and qualitative data were collected in
this study. 75 undergraduates from three tutorial groups from an academic writing course at a
Malaysian private institution of higher learning were selected as the experimental and
control groups through purposive sampling. The quasi-experimental pre-test-post-test design was
employed to collect the undergraduates’ scores on argumentative essays while qualitative data were
gathered using three methods, which were observation, focus group interview and one-to-one
interview. The Pearson product-moment correlation and paired samples t-test were used for
quantitative data analysis while thematic analysis was used for qualitative d.....