Risk-taking propensity can be influenced by sensation-seeking traits and self-perceived invincibility. We hypothesized that the latter factor may reflect a stable trait that endures across situations and may influence risk-taking behavior. We developed and validated a 20-item scale, the Invincibility Belief Index (IBI) to measure this construct. The IBI demonstrated good internal consistency and excellent test-retest reliability in the development sample (n = 100) and sustained similar levels of reliability in a cross-validation sample (n = 74). Principal components analysis yielded three orthogonal factors measuring self-perceived impunity (immunity from consequences), boldness/audacity (self-assuredness and competitiveness), and adroitness (mental agility and survival skill). In the prediction of risk taking, IBI scores contributed additional unique variance beyond sensation-seeking scores alone. IBI scores demonstrated convergent and discriminant validity with concurrently administered measures. These preliminary results support the reliability and validity of the IBI as a brief measure of self-perceived vulnerability-invincibility in the face of adversity.