Objective: Low IQ has recently been shown to predict effort test failure in healthy and neurological populations. Although low IQ is common in schizophrenia (SZ), its effect on effort test performance remains unclear. Method: Participants included 60 outpatients with SZ and 30 demographically matched healthy controls (CN) who received a battery of neuropsychological tests. Insufficient effort was calculated using the Digit Span Age-Corrected Scaled Score Effort Index and the Finger Tapping Effort Index. Results: A total of 33.3% SZ and 6.7% CN fell below the Digit Span Age-Corrected Scaled Score Effort Index cut-off χ2(1, 89) = 7.70, p < 0.01, and 35.7%SZ and 3.3% CN fell below the Finger Tapping Effort Index cut-off χ2(1, 85) = 11.10, p < 0.001. Conclusion(s): Low IQ is a significant predictor of falling below effort cut-off scores for indices embedded in standard neuropsychological tests. IQ may complicate the interpretation of effort testing in SZ patients who may have low motivation, but are not feigning cognitive impairment.