Objective: Patients with end-stage renal disease are required to limit fluid and salt intake. We examined illness representations [common-sense model (CSM)] among a sample of hemodialysis (HD) patients, investigating whether fluid-adherent patients held illness representations different from those of nonadherent patients. We also explored the utility of illness perceptions in predicting fluid nonadherence after controlling for clinical parameters, including residual renal function (KRU). Methods: Illness perceptions were assessed [Revised Illness Perception Questionnaire (IPQ-R)] in 99 HD patients. Clinical parameters were collected and averaged over a 3-month period prior to and including the month of IPQ-R assessment. Depression scores, functional status, and comorbidity were also collected. Fluid nonadherence was defined using interdialytic weight gain (IDWG) and dry weight (ideal weight). Patients in the upper quartile of percent weight gain were defined as nonadherent (IDWG≥3.21% dry weight). Results: Nonadherent patients had timeline perceptions significantly lower than those of adherent patients. Logistic regression models were computed in order to identify predictors of fluid nonadherence. After several demographic and clinical variables, including age, gender, and KRU, had been controlled for, lower consequence perceptions predicted nonadherence. Conclusions: Illness representations appear to predict fluid nonadherence among HD patients. Extending the CSM to investigate specific perceptions surrounding treatment behaviors may be useful and merits attention in this setting.