Counterfactual emotions, such as regret and relief, require an awareness of how things could have been different. We report a pre-registered experiment that examines the real-time understanding of counterfactual emotions in adults with and without ASD, based on research showing that the developmental trajectory of counterfactual thinking may be disrupted in people with ASD. Participants were eye-tracked as they read narratives in which a character made an explicit decision then subsequently experienced either a mildly negative or positive outcome. The final sentence in each story included an explicit remark about the character’s mood that was either consistent or inconsistent with the character’s expected feelings of regret or relief (e.g. “… she feels happy/annoyed about her decision.”). Results showed that adults with ASD are unimpaired in understanding emotions based on counterfactual reasoning, and in fact showed earlier sensitivity to inconsistencies within relief contexts compared to TD participants. This finding highlights a previously unknown strength in empathy and emotion processing in adults with ASD, which may have been masked in previous research that has typically relied on explicit, response-based measures to record emotional inferences, which are likely to be susceptible to demand characteristics and response biases. This study therefore highlights the value of employing implicit measures that provide insights on peoples’ immediate responses to emotional content without disrupting ongoing processing.