Aim: The aim of the current investigation was to detect serotypes of Aggregatibacter actinomycetemcomitans in a cohort of Western Australians diagnosed with periodontitis. Materials and Methods: A total of 64 subjects were selected. Intra-oral samples were taken from every subject in the present investigation. Periodontal, radiographical, and microbiological analyses were conducted. A polymerase chain reaction was employed to investigate the presence of Aggregatibacter actinomycetemcomitans serotypes. Results: Only twelve (18.75%) patients were tested positive for Aggregatibacter actinomycetemcomitans. The most dominant serotypes of Aggregatibacter actinomycetemcomitans in this group were serotype e (80.55%), followed by serotype c (52.77%). Both serotypes b and d were absent in the present investigation. Serotype e presented in isolation or combined with other serotypes. The other serotypes tend to be present alone, but when they were isolated together, they were always combined with serotype e. It seems that serotype e of Aggregatibacter actinomycetemcomitans is associated with those who live in rural areas (p = 0.003), and those with low education (p = 0.041), and severe forms of periodontitis in this cohort. Conclusions: In patients diagnosed with severe periodontitis, serotype e was dominant in this population. Serotypes b and d did not appear in the present study.