Dealing with numbers is an inherent aspect of interpreting health statistics, and negative emotions may interfere with medical decision making. One emotionally charged decision-making context is parents making medical decisions for their children. Knowing which factors--such as anxiety specific to math contexts--are associated with parents' negative emotions during the decision-making process may inform ways to better support families as they make critical medical decisions. The current study involved secondary data analyses of an experiment with 249 parents. Participants were randomly assigned to make hypothetical health decisions for themselves, their child, or a stranger. We examined which domain-specific math (e.g., math anxiety), domain general (i.e., need for cognition), and demographic variables (e.g., parents' health-care coverage) were associated with ratings of negative emotional activation immediately after making the decisions. Results indicated that two factors were significantly associated with parents' ratings of negative emotional activation: (1) the person they were making decisions about (i.e., higher negative emotion activation if they were randomly assigned to make hypothetical health decisions about their child versus themselves or a stranger), and (2) parents' ratings of their own math anxiety (i.e., parents with higher self-reported math anxiety also reported higher negative emotional activation). Future research may further consider the joint roles of emotional activation and math anxiety in how parents make health decisions for their children. Further, understanding how much math anxiety causally contributes to people's overall negative emotional activation could lead to a more nuanced understanding of negative emotional activation in health decision making.