Purpose The Patient Assessment of Chronic Illness Care (PACIC) was created to assess whether provided care is congruent with the Chronic Care Model, according to patients. We aimed to identify all studies using the PACIC in diabetic patients to explore (i) how overall PACIC scores varied across studies and (ii) whether scores varied according to healthcare delivery, patient and instrument characteristics. Data sources MEDLINE, Embase, PsycINFO, CINAHL and PubMed Central (PMC), from 2005 to 2016. Study selection Studies of any design using the PACIC in diabetic patients. Data extraction and synthesis We extracted data on healthcare delivery, patient, and instrument characteristics, and overall PACIC score and standard deviation. We performed random-effects meta-analyses and meta-regressions. Results We identified 34 studies including 25 942 patients from 13 countries, mostly in North America and Europe, using different versions of the PACIC in 11 languages. The overall PACIC score fluctuated between 1.7 and 4.2, with a pooled score of 3.0 (95% confidence interval 2.8–3.2, 95% predictive interval 1.9–4.2), with very high heterogeneity (I2 = 99%). The PACIC variance was not explained by healthcare delivery or patient characteristics, but by the number of points on the response scale (5 vs. 11) and the continent (Asia vs. others). Conclusion The PACIC is a widely used instrument, but the direct comparison of PACIC scores between studies should be performed with caution as studies may employ different versions and the influence of cultural norms and language on the PACIC score remains unknown.