We assessed the onset of malignant and nonmalignant complications in a cohort of celiac disease (CD) patients under gluten-free diet (GFD). Five hundred and forty-nine CD patients were retrospectively assessed. Two hundred and fifty-one (45.7%) showed classical, 262 (47.7%) subclinical, and 36 (6.6%) silent form of CD at the time of the diagnosis. The mean time under GFD was 7.13 years (range 1-15 years). Out of 549 patients, 381 (69.4%) were fully compliant, 112/549 (20.4%) reported less than one dietary transgression/month, and 56/549 (10.2%) reported at least one dietary transgression/month. Out of 549 patients, 18 (3.3%) patients developed complications under GFD (seven malignant and 11 nonmalignant complications). Fourteen patients were previously affected by classical CD (5.6% of the overall patients with classical CD), and four were affected by subclinical CD (1.5% of the overall patients with subclinical CD). None of the patients affected by silent CD developed complications. There was no statistical difference between the mean age of the two groups developing complications (P = n.s.). Complications appeared after a mean time under GFD of 6.5 years in classical CD, and after a mean time of 3.5 years in subclinical CD (P = n.s.). Finally, 6/14 (42.8%) patients with classical CD were not fully compliant to GFD, while 2/4 (50%) of subclinical CD patients were not fully compliant to GFD (P = n.s.). Less than 5% of CD patients may develop complications under GFD. Complications seem to affect more classical CD than subclinical CD, and seem to be irrespective of optimal GFD adherence.