Job performance is considered the “ultimate dependent variable” in human resource management, turning its assessment into a capital issue. The present study analyzes the functioning of a brief 18-item self-report scale, the Individual Work Performance Questionnaire (IWPQ), which measures the main dimensions of job performance (task performance, contextual performance, and counterproductive behaviors) in a wide variety of jobs. Participants were 368 employees who voluntarily answered a questionnaire including the IWPQ, other performance scales, and the NEO-FFI. Descriptive statistics, exploratory structural equation modeling, and correlations were performed. Results show that the IWPQ has a tridimensional structure with adequate reliability, exhibits significant associations with other measures of performance, and its association with personality traits is similar in terms of direction and strength of the correlations between other job performance measures and personality. We conclude that the IWPQ is an adequate measure of job performance but with emphasis on behaviors aimed toward organizations.