The aim of this study was to assess the level of knowledge among adult men regarding male fertility, with particular emphasis on selected factors connected with medical and lifestyle-related aspects of fertility. The results provide a strong basis for further research aimed at identifying knowledge gaps in male infertility and developing effective educational strategies. The study was performed in 156 men of reproductive age. An anonymous questionnaire developed by the authors was used, consisting of two sections: a demographic section and 25 single-choice questions assessing the subjects’ knowledge in the area of medical and lifestyle-related aspects of male fertility. The results revealed the existence of a weak positive correlation between the level of knowledge about male fertility and age. Moreover, the level of fertility-related knowledge was higher in those participants who had an education in a field connected with medicine as well as in men suspected of or treated for infertility. Another novel finding is that although many respondents expressed an interest in health—as evidenced in their declaring the use of dietary supplements—this was not reflected in their performance in the questionnaire. This highlights the gap between health-related decisions and limited fertility literacy. In general, the findings show that the participants’ level of knowledge concerning male fertility was inadequate in most areas—both medical and lifestyle-related—covered by the questionnaire. Based on the findings of the study, relevant recommendations for educational initiatives were proposed, which could potentially improve fertility awareness among men.