Background: This study aimed to examine the characteristics of older adults patients who suffered a head injury after a ground-level fall in comparison to non-head injury patients as well as the factors associated with severity in those with head injury only. Methods: Patients were classified into two groups, the head injury group and the non-head injury group. The characteristics were compared and factors associated with head injury were evaluated. Factors relating to severe injury in the head injury group were also investigated. Results: The head injury group comprised 42 % of a study subjects. Male sex; fall time of 18:00–23:59; fall location of medical facility, transportation area, and public or commercial facility; fall in an outdoor area; fall during daily activity; alcohol ingestion; fall from stairs; non-slippery floor conditions; concrete flooring; sloped flooring; and presence of obstacles on the floor were risk factors for head injury in the older adults after a ground-level fall. Male sex and age over 70 years; fall time of 00:00–05:59; fall in a residential facility; fall in an indoor area; fall during daily activity; fall from stairs; non-slippery floor conditions; and presence of obstacles on the floor were factors associated with severe injury in the head injury group. Conclusions: Male sex with advanced age, indoor fall, and the presence of obstacles on the floor were risk factors for severe injury in the head injury group in older adults individuals who suffered a ground-level fall. It is necessary to develop appropriate ground-level fall prevention programs by evaluating the individual and environmental characteristics of older adults patients.