Indiana University-Purdue University Indianapolis (IUPUI) / Pancreatic cancer is the third leading cause of cancer-related deaths and is projected to rank second by 2030 in the United States. However, the etiology of this malignancy remains elusive, with family history, chronic pancreatitis, type 2 diabetes, and cigarette smoking as only established risk factors. Therefore, it is urgent and important to identify risk factors, especially modifiable ones (e.g. diet), for the primary prevention of this lethal disease. In this dissertation, we have investigated the associations of mineral intake, dietary quality, and body adiposity with the risk of pancreatic cancer among participants in the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) Screening Trial. Calcium, magnesium, and phosphorus are essential minerals that modulate energy metabolism and glucose homeostasis and may thus be involved in pancreatic carcinogenesis. In the first manuscript, we found that total calcium intake was associated with a reduced risk of pancreatic cancer. In addition, a significant linear inverse association was observed for total magnesium intake. The Healthy Eating Index, 2015 (HEI-2015) and the Dietary Quality Index- revised (DQI-R) have been developed to assess the overall quality or patterns of diet. In the second manuscript, we did not find significant associations between HEI-2015 or DQI-R scores and pancreatic cancer risk. However, a higher intake of some score components (i.e., calcium, vegetables, and whole grains) conferred a lower risk. Although mounting biological mechanisms have linked overweight and obesity to the development of pancreatic cancer, it is largely unclear whether prediagnostic body mass index (BMI) trajectory is associated with the risk of this disease. In the third manuscript, we revealed that prediagnostic adulthood BMI trajectory was not associated with pancreatic cancer risk, but a suggestively or significantly increased risk were identified for individuals who were overweight at age 20 or obese at age 50, compared with those who had a normal weight at the two respective time points. Taken together, the findings of research presented in this dissertation contribute to an improved understanding of the crucial roles of diet and adiposity in the etiology of pancreatic cancer, which may offer some new avenues for the prevention of this intractable malignancy.