Objectives: To study the relationship between coping strategies and nausea during emetogenic pelvic-abdominal radiotherapy, and to describe the patients’ rationales for their expectations regarding nausea. Methods: Patients (n = 200: 84% women, mean age 64 years, 69% had gynecological, 27% colorectal, and 4% had other malignances) longitudinally participated during pelvic-abdominal radiotherapy. We measured adopted coping strategies using the Mental Adjustment to Cancer scale and the patients’ rationales for their expectations regarding nausea at baseline. The patients registered nausea and vomiting daily during the radiotherapy period (mean 36 + Standard Deviation 10 days). Results: Patients who experienced nausea (n = 128, 64%) during the radiotherapy period graded a lower score on “Fighting Spirit” (median, md, score 51, P = .031) and a higher score on “anxious preoccupation” (md 18, P = .040) compared to patients who did not experience nausea (n = 72, 36%), md 54 and md 17. More of the patients for whom “Helpless-Hopeless” represented the most predominant response experienced nausea (100%) or vomited (56%) compared to patients adopting “Fighting Spirit”: 62% experienced nausea (P = .011) and 20% vomited (P = .014). Only four (6%) of the nausea-free patients had expected themselves to be at increased risk for nausea. Of the patients who became nauseous, 22 (17%) patients had expected themselves to be at increased risk for nausea (P = .017), based on previous experience. Conclusion: Patients adopting maladaptive coping strategies or patients expecting nausea based on previous experiences, were more likely to experience nausea than other patients when undergoing emetogenic pelvic-abdominal radiotherapy. Cancer care professionals may identify patients adopting maladaptive coping strategies or having high nausea expectations by applying the MAC scale and self-assessment of expected nausea risk and guide these patients to adopt adaptive coping strategies and strengthen their expectations on successful prevention of nausea.Trial registration number: Clinicaltrials.gov: NCT00621660.