The aim of the study was to understand how lottery incentives influenced the HIV counselling and testing (HCT) behaviour and behaviour intention of shop-floor workers who participated in a workplace HCT campaign initiative in two companies in the Nelson Mandela Bay municipality, South Africa. A post-test only quasi-experimental approach was used. The data were first collected, using a self-administered cross-sectional survey instrument, among the control group (n = 88) followed by the experimental group (n = 110) after the advent of HIV testing and lotteries was announced. HIV testing behaviour data were collected on the days of the HIV testing events. The theory of planned behaviour (TPB) was used as guiding theory. Principal component analysis (PCA), t- and chi-square tests, and logistic regression were conducted to analyse the data. A significant increase in the mean scores of the experimental as compared to the control condition for the subjective norm's construct (t = -3.55, p < 0.001) and HIV testing behaviour intention (χ2 = 12.35, p < 0.001) was measured following the announcement of lottery incentives. The constructs of TPB explained 40% of the variance in HCT behaviour intention (R2 = 0.40). The strongest predictor of behaviour intention was the subjective norm (B = 0.435 and p < 0.001), followed by the attitudinal component (B = 0.323 and p = 0.040). The announcement of lotteries made shop-floor workers develop a stronger intention to participate in workplace HIV testing through anticipation of stronger social support and encouragement. It was not possible to link behaviour intention to behaviour due to missing data. The findings point to the importance of providing workers with an opportunity to openly discuss HIV testing thus allowing mitigation of HIV stigma and discrimination and permitting HIV testing to become socially sanctioned and seen as part of a collective effort.