Predictors of effort test failure were examined in an archival sample of 555 traumatically brain-injured (TBI) adults. Logistic regression models were used to examine whether compensation-seeking, injury-related, psychological, demographic, and cultural factors predicted effort test failure (ETF). ETF was significantly associated with compensation-seeking (OR = 3.51, 95% CI [1.25, 9.79]), low education (OR:. 83 [.74, . 94]), self-reported mood disorder (OR: 5.53 [3.10, 9.85]), exaggerated displays of behavior (OR: 5.84 [2.15, 15.84]), psychotic illness (OR: 12.86 [3.21, 51.44]), being foreign-born (OR: 5.10 [2.35, 11.06]), having sustained a workplace accident (OR: 4.60 [2.40, 8.81]), and mild traumatic brain injury severity compared with very severe traumatic brain injury severity (OR: 0.37 [0.13, 0.995]). ETF was associated with a broader range of statistical predictors than has previously been identified and the relative importance of psychological and behavioral predictors of ETF was evident in the logistic regression model. Variables that might potentially extend the model of ETF are identified for future research efforts.