<p>Valence is a common feature across emotion theories and is often described using a simple positive versus negative dimension. Whereas many circumstances elicit relatively consistent categorizations of positivity and negativity across people, there are other conditions when the valence of a stimulus is ambiguous and thus defies this simple, uniform categorization. In this short review, we will describe research investigating individual differences in interpretations of valence ambiguity to support the notion that valence is not an invariant feature of a stimulus, but rather arises from diverse appraisals that can be learned, challenged, and changed. These individual differences are referred to as valence or interpretation biases and defined as the tendency to evaluate ambiguous emotional stimuli as more positive or negative. Valence bias has been associated with affective traits, psychosocial functioning, and brain organization, demonstrating trait-like stability that, nonetheless, is malleable during targeted interventions including treatment for mental health disorders. Collectively, studies of valence ambiguity highlight the variable nature of valence interpretations across people, supporting the notion that valence itself is a multifaceted construct uniquely determined by the perceiver in a given context. Future research should further probe valence ambiguity in real world conditions and better characterize individual differences in the origins, limits, and implications of biased valence interpretations.</p>