Math anxiety has received increasing focus in recent years, yet the causes for developing math-anxiety remain unclear. Whereas previous research focused on physiological/environmental causes, we examine the link between math-anxiety, dispositional mindfulness, and self-centeredness (operationalized as self-prioritization and decentering). The experiment was performed by 81 participants, and included the original perceptual shape-matching task, measuring the self-prioritization effect, and our novel perceptual number/equation-matching tasks, developed to examine self-prioritization under math-anxiety activation. We also measured math-anxiety, dispositional mindfulness, and decentering (self-reports). We showed that (a) math anxiety was significantly and negatively correlated with dispositional mindfulness and decentering (though there was no correlation between self-prioritization and dispositional mindfulness); (b) self-prioritization was reduced among high math anxiety participants under math-anxiety activation only in the number-matching task (main finding); and (c) decentering was significantly correlated with self-prioritization in the number-matching task, stemming from the low math anxiety group. Our study is the first to indicate a link between math-anxiety, dispositional mindfulness, and self-centeredness. Discussing the main findings, we suggest three interpretations: (a) Negative mood induction may reduce self-prioritization by turning attention to internal states rather than to the stimuli; (b) math-anxiety activation may reduce emotional valence, which in turn reduces the advantage of self-processing; and (c) disruption of self-prioritization by induced negative mood can be due to a breakdown of the integrated-self (previously conceptualized as a high degree of connectedness between the cognitive/affective/motivational/behavioral systems).