Background: Experiencing a myocardial infarction threatens the health and life of the patient; therefore, it can be perceived as a traumatic event. Indeed, myocardial infarction may result in negative consequences, including symptoms of posttraumatic stress disorder (PTSD). However, it is also possible to experience positive effects from traumatic events, which is expressed as posttraumatic growth. Personality characteristics, including type D (i.e., distressed) personality, are among several factors that have been shown determine the occurrence of negative and positive consequences after exposure to trauma. Aim of the study: The aim of the present study was to establish the role of distressed personality in the occurrence of negative and positive effects of trauma resulting from myocardial infarction. Material and methods: The study included a total of 80 patients after myocardial infarction. Sixty-three patients aged 43–85 years (M=67, SD=10.76) were included in the final analysis. The majority of respondents were men (61.9%). Patients completed a survey with three standardized measurement tools: the PTSD Checklist for DSM-5 (PCL-5), the Posttraumatic Growth Inventory (PTGI), and the Type D Scale (DS-14). Results: Negative affectivity was positively associated with PTSD symptoms, and this association was strongest for negative changes in cognition or mood. Social inhibition was not associated with PTSD symptoms, except for increased arousal and reactivity. Both dimensions of type D personality were positively related to one factor of posttraumatic growth: changes in the spiritual sphere. Conclusions: Reducing the severity of negative affectivity may decrease PTSD symptoms and thus contribute to improved psychosocial functioning among patients who have experienced myocardial infarction.