Hyperemesis gravidarum is the most severe form of nausea and vomiting in pregnancy that seriously affects the pregnancy outcome. It is a disease with unknown etiology and varieties of contributing factors like hormonal changes, psychological and immunological factors. A significantly high prevalence of Helicobacter pylori among pregnant women with Hyperemesis gravidarum has been revealed recently. A descriptive, cross-sectional study was carried out at antenatal ward, Department of Obstetrics and Gynaecology, Mymensingh Medical College Hospital, Mymensingh for a period of twenty-one months among purposively selected thirty-six patients with Hyperemesis gravidarum with a view to assess the involvement of H. pylori in Hyperemesis gravidarum. Data were collected through interview, physical examinations and laboratory investigations by using case record form. Statistical analysis was performed using SPSS version 20.0 for Windows. Highest number 16(44.44%) of respondents were in age group 20 to 24 years with a mean of 23.81 years and a standard deviation (SD) of 4.55 years. Majority 29(80.56%) of the women had education less than 12 years, as many as 28(77.78%) women were housewives, and at least 14(38.89%) women had unplanned pregnancies. An overwhelming majority 29(80.56%) of women had their pregnancy duration between 8 to 12 weeks with a mean duration of 10.64 weeks and a standard deviation of 2.35 weeks. Majority 20(55.56%) of women were pregnant for first time, as many as 19(52.78%) women had duration of illness for 5 to 9 weeks. Of 16 multi-gravid women, 7(43.75%) had history of similar condition in their previous pregnancies. As many as 9 (25.00%) women had family history of similar condition in their mothers and sisters. First trimester was time of manifestation of the condition.At least 11 (30.56%) stool samples were positive for H. pylori stool antigen. Family history of Hyperemesis gravidarum and presence of H. pylori stool antigen are statistically associated (p<0.05). Pregnancy at young age, low educational status of women, nulliparity, unplanned pregnancy, past history, family history and H. pylori infection are the identified risk factors of Hyperemesis gravidarum.