Invasive Streptococcus anginosus group (SAG) infection is associated with severe infection and poor outcome particularly among malignancy and post-surgical patients. We aimed to study the clinical details and outcomes of invasive SAG infection in post-sleeve surgery and malignancy related and non-malignancy related abdominal infections. (SAG) isolates from invasive infections between January 2015 and February 2018 were collected. Clinical data from the medical records of the infected patients were obtained retrospectively and analyzed. Fourteen invasive infections caused by SAG were identified. The mean age of the patients was 40.9 (minimum; 18 years, maximum; 80 years, SD; 21.03), five females (35.7 %) and nine (64.3 %) males. The peritoneal fluid was the most common specimen (8/15; 53.3%), followed by pleural fluid (3/15; 20%), deep abscesses (2/15; 13.3%), blood (1/15; 6.7%) and ascetic fluid (1/15; 6.7 %). The most predominant specimens (73.3%) were intra-abdominal involving commonly anaerobes and Enterobacteriaceae. Six patients (6/14; 42.9 %), had SAGabdominal or pleural infection as a complication of sleeve surgery. Each four of the remaining eight patients were categorized as patients with abdominal malignancy (4/14; 28.6 %) or non-malignancy related abdominal infections (4/14; 28.6%). Ten of the cases had polymicrobial infection. All patients had eventual recovery except of two malignancy patients who died because of severe sepsis with empyema or abdominal infection. Further studies are required to delineate post-operative sleeve surgery infectious complications and malignancy related abdominal infections to provide early treatment and better outcome.