Attributional ambiguity is a strategy used to avoid having to attribute potentially negative performance on a task to ability. If the outcome of a task is attributable to ability, if no external cause for failure is available, and if a person is aware that the outcome is attributable to the self, ambiquity can be created with regard to the causation of the outcome. Heightened attribution of an outcome to self, as results from self-focused attention, was expected to produce less effort when external causes for potential failure were explicitly removed. In a 2 × 2 experiment, a positive mood was induced that was then either suggested or excluded as a plausible explanation for potential failure on a task said to be indicative of general intellectual ability. Subjects for whom self-awareness was experimentally induced, and for whom an external attribution of failure was explicitly removed, put significantly less effort into the task. Self-focus, however, has also been shown to enhance task performance. An indirect measure showed increased readiness to perform in direct contrast to the obtained lower self-reports of effort. The range of generalizability and application of attribute ambiguity is discussed.