Digit ratio (2D:4D; a putative correlate of prenatal testosterone) has been shown to be predictive of important personality factors such as mental toughness, optimism and academic achievement. However, to date no study has attempted to investigate prenatal testosterone levels as a predictor of GRIT (persistency and constancy) and the Big 5 personality traits Openness to experience, Conscientiousness, Extraversion, Agreeableness and Neuroticism. Research has also alluded to the potential gender and cultural differences in biological underpinnings of psychological functioning. This study included a sample of Dubai and UK undergraduate students and examined associations between prenatal testosterone (2D:4D), GRIT and Big 5 personality traits (openness to experience, conscientiousness, extraversion, agreeableness and neuroticism). UK and Dubai participants followed the same testing procedure and completed a self-report measure for GRIT and Big 5 personality traits, followed by providing a right-hand scan, which was later used to measure 2D:4D using Vernier Callipers. Results showed that in Dubai participants, the measured psychological variables explained a greater amount of variance in 2D:4D than in UK participants. Openness to experience was a strong significant predictor of 2D:4D in Dubai participants whereas, GRIT, conscientiousness and openness to experience were all significant predictors of 2D:4D for UK participants.