The patients’ sexual life after a myocardial infarction is important for his/her quality of life. In spite of this, many patients are in doubt regarding their sex life after a myocardial infarction (MI) and the sexual information received, and counselling from health care providers has been seen to be insufficient. The purpose of this study was to evaluate the psychometric properties of ‘The 25-item Sex after MI Knowledge Test’ in a Swedish context. A convenience sample was recruited. The scale was translated into Swedish and completed by 79 former patients from The Heart and Lung Patients’ National Association on two occasions, with an interval of 2 weeks. The scale was tested for face and content validity, internal consistency and test–retest reliability. The result in this study indicates that the instrument has good face and content validity and displayed a moderate internal consistency (alpha 0.61). The instrument showed some level of instability in test–retest reliability with 60% of the items presenting moderate or strong agreement between the test and retest. Further studies that use this instrument in larger and more diverse samples are thus needed.