Family members' diabetes-specific obstructive behaviors (e.g., nagging/arguing or getting in the way of patients' self-care) are associated with adults having worse glycemic control (HbA1C), with diabetes-specific supportive family behaviors protecting against this detrimental effect. Given the role of family members in helping patients with limited health literacy, patients' health literacy status may moderate these relations. The authors tested this hypothesis with 192 adults with type 2 diabetes. Twenty-six percent had limited health literacy, and limited health literacy was associated with more supportive family behaviors (p<.05), but not with obstructive family behaviors or with patients' HbA1C. Adjusted stratified analyses indicated obstructive family behaviors were more strongly associated with worse HbA1C among participants with limited health literacy and low supportive family behaviors than for participants with adequate health literacy and low supportive family behaviors (adjusted simple slopes β=0.70, p=.05 vs. β=0.36, p=.009). However, there was no association between obstructive family behaviors and HbA1C in the context of high supportive family behaviors, regardless of health literacy status. Involving family members in adults' self-care without teaching them to avoid obstructive behaviors may be particularly harmful for patients with limited health literacy. Future research should identify intervention content to reduce obstructive family behaviors and identify which supportive family behaviors may be protective.