While patients with poor functional health literacy (FHL) have difficulties reading and comprehending written medical instructions, it is not known whether these patients also experience problems with other modes of communication, such as face-to-face encounters with primary care physicians. We enrolled 408 English- and Spanish-speaking diabetes patients to examine whether patients with inadequate FHL report worse communication than patients with adequate FHL. We assessed patients' experiences of communication using sub-scales from the Interpersonal Processes of Care in Diverse Populations instrument. In multivariate models, patients with inadequate FHL, compared to patients with adequate FHL, were more likely to report worse communication in the domains of general clarity (adjusted odds ratio [AOR] 6.29, P<0.01), explanation of condition (AOR 4.85, P=0.03), and explanation of processes of care (AOR 2.70, p=0.03). Poor FHL appears to be a marker for oral communication problems, particularly in the technical, explanatory domains of clinician-patient dialogue. Research is needed to identify strategies to improve communication for this group of patients.