The ability to distinguish between truthful and deceptive statements has been argued to be essential for social workers. The present study investigated the relationship between occupational experience, suspicion level, situational familiarity, judgemental truth or lie bias, and social workers’ accuracy in detecting lie and truth. Each of the 125 social workers, whose role is to counsel the unemployed, rated fourteen video fragments of stimulus persons who either told the truth or lied about a job they had been working in. In line with previous research, occupational experience was not related to overall classification accuracy of true and deceptive messages. Further results indicate that suspicion level increases lie detection accuracy, whereas situational familiarity increases truth detection accuracy. Moreover, the effect of suspicion level on lie detection was mediated by lie bias. Practical implications are discussed.