Evidence has been accumulating that shows the promise of multidimensional conceptualizations of anxiety in investigating the effects of anxiety on different aspects of human behavior and intellectual performance. In view of the lack of an L2 writing anxiety scale explicitly developed from a multidimensional perspective, this study aims to develop and evaluate a self-report L2 writing anxiety measure that conforms to a three-dimensional conceptualization of anxiety. Sixty-five EFL learners' reports of L2 writing anxiety were drawn upon to generate an initial pool of scale items. A pilot test was conducted on the initial pool of items to help establish a preliminary version of L2 writing anxiety scale for further refinement and evaluation in the formal study. A sample of 421 EFL majors enrolled in seven different colleges in Taiwan participated in the formal study. Exploratory factor analysis was employed to determine the final make-up of the Second Language Writing Anxiety Inventory (SLWAI) that consists of three subscales: Somatic Anxiety, Cognitive Anxiety, and Avoidance Behavior. In addition to reliability coefficients, the validity of the SLWAI total scale and subscales was assessed by means of correlation and factor analysis. The results suggest that both the total scale and the individual subscales of the SLWAI have good reliability and adequate validity.