Introduction: We evaluate the association between caregiver (informal) time/cost and illness severity from two recently completed clinical trials of an investigational drug for Alzheimer’s disease (AD). Methods: Changes from baseline caregiver time were calculated and treatment effects analyzed using a restricted maximum likelihood-based mixed model for repeated measures. Four separate models were then estimated to examine the association between caregiver time costs and the clinical endpoints measured during the trials, including cognition (MMSE), function (DAD), behavior (NPI), global disability (CDR) and dependence (DS). Results: Caregiver time cost was significantly associated with all clinical measures of illness severity with a 1-unit change in MMSE, DAD, NPI, CDR and DS associated with a 11.57%, 4.81–4.97%, 3.58–3.67%, 42.52% and 71.05% change, respectively, in primary caregiver time cost. The association between caregiver time cost and DS was the strongest of all the associations examined. Conclusion: Caregiver time costs increase with increasing AD severity in all key domains of AD (cognition, function, behavior, global disability and dependence on others). Our analysis demonstrated that patient dependence is a particularly important predictor of caregiver time costs and should be considered as a potential outcome measure in intervention clinical trials in AD. Funding: Pfizer Inc. and Janssen Alzheimer Immunotherapy Research and Development.