We conducted a meta-analysis of studies reporting diabetes case management interventions to examine the impact of case management on blood glucose control (HbA1c). Databases used for the search included Medline, PubMed, Cochrane EPOC, Cumulative Index to Nursing & Allied Health Literature database guide (CINAHL), and PsychInfo. A composite estimate of effect size was calculated using a random effects model and subgroup analyses were conducted. Twenty-nine salient studies involving 9397 patients had sufficient data for analysis. Mean patient age was 63.2 years, 49% were male, and ethnicity/race was 54% White. Type 2 diabetes was the focus in 91% of studies. Results showed a large overall effect size favoring case management intervention over controls or baseline values on HbA1c (ES=0.86, 95%CI: 0.52-1.19, Z=5.0, p<0.001). This corresponds to a mean HbA1c reduction of 0.89 (95%CI: 0.63-1.15). Subgroup analyses showed clinical setting, team composition, and baseline HbA1c were important predictors of effect size, but not diabetes self-management education which was poorly described or absent in most diabetes case management interventions examined. Nurse-led case management provides an effective clinical strategy for poorly controlled diabetes based on a meta-analysis of clinical trials focusing on blood glucose control.