In patients with low back pain (LBP), physical functioning may be negatively influenced by both expectations on pain and pain-related fear. It is unclear whether these factors influence both physical functioning in the laboratory as well as in daily life. The aim of this study was to test if a combination of persistent overprediction of pain and fear of movement predicts lab-based performance and whether these factors are relevant for predicting daily-life functioning. One hundred and twenty four patients with subacute LBP performed a laboratory-based performance test twice. Maximum voluntary contraction, pre-test pain expectations, perceived pain during testing and fear of movement were measured. Patients were classified as correct or incorrect predictors, based on differences between expected and perceived pain on the second attempt. Next, physical activity in daily life was measured with an accelerometer. In explaining physical functioning in the laboratory and in daily life an interaction effect between fear and pain prediction was observed. In overpredictors, fear was negatively associated with lab-based performance (beta = -0.48, p <0.01), and positively associated with daily-life functioning (beta = 0.50, p <0.05). No significant association between fear and performance or daily-life functioning were found in correct predictors. In contrast to correct predictors, in overpredictors lab-based performance and daily-life functioning was additionally explained by fear of movement. Thus it appears that fear of movement is only predictive of performance in patients with LBP who simultaneously overpredict the consequences of movements in terms of painfulness.