Since February 2017 in Poland, an increasing number of acute hepatitis A (AHA) cases have been reported; a noteworthy increase to 3,072 cases of AHA in 2017 compared to 35 cases in 2016 was reported by the National Institute of Public Health (NIPH). The aim of this study was to evaluate the demographic features, clinical manifestations, laboratory results, and sexually transmitted coinfections. All cases of AHA diagnosed between February 2017 and February 2018 at the University Hospital in Krakow were analyzed. A total of 119 cases of hepatitis A virus (HAV) were reported; 105 (88%) were males and 14 (12%) were females, with a mean age 31 years (range 19–62). In 84 patients (71%), the HAV was transmitted by oral–anal sexual contact between men. Six women were infected by close house contact with men infected with HAV. The route of transmission was not identified for 29 cases, and 88 patients (74%) required hospitalization. Among the cases, the following coinfections were already diagnosed: HIV 36 patients (30%), chronic hepatitis C virus (HCV) 4 patients (3%), and chronic hepatitis B virus (HBV) 2 patients (1.5%). During AHA diagnosis, some new sexually transmitted infections (STIs) were detected; syphilis eight patients (6.7%), HIV/syphilis seven patients (6%), HIV//HCV/syphilis one patient, and acute retroviral syndrome/ Shigella flexneri one patient. Overall, AHA outbreak in Poland in 2017 affected primarily men who have sex with men (MSM) and was connected with oral–anal sexual contacts, and the majority of patients did not have HAV vaccination. These results show a clear need for routinely offering HAV vaccination to at-risk populations and that awareness among health-care workers about HAV sexual transmission may help introduce prevention methods.