Background: Diabetic peripheral neuropathy (DPN) is a severe complication of diabetes mellitus (DM). Measurement of plantar fascia thickness by ultrasound has been proposed as an alternative index of tissue glycation and a marker of diabetes complications such as DPN. Aim: The primary objective was to compare the thickness of plantar fascia in T1DM patients with healthy volunteers. The secondary objective was to correlate thickness plantar fascia with clinical parameters. Methods: A cross-sectional study was conducted in 274 patients with T1DM (2.3 [2-2.8] age 53 [20-87] years and diabetes duration 28 [1-79] years and 41 healthy volunteers (1.7 [1.6-2.05] age 49 [26-73] years). Plantar fascia thickness was measured during outpatient clinical evaluation by means of right foot ultrasound. Upper normal values were set at the 90th percentile of control subjects. The values were compared with clinical and demographic data, Advanced Glycation End Products (AGEs) measured by skin autofluorescence, and parameters derived from clinical evaluation of DPN: vibrotactile sense by biothesiometer, touch/pressure perception by 10-g monofilament, dorsal pedal and posterior tibial artery pulse, Lunge test, and assessment of risk category. Results: T1DM patients had significantly thicker plantar fascia than controls (2.9 [2.5-3.2] mm vs 2.4 [2.3-2.5] mm; p<0.001); 186/274 (68%) T1DM patients had altered plantar fascia thickness. The difference remained statistically significant even after adjustment for age and sex. Correlations between each sensory test for the assessment of diabetic foot neuropathy, levels of HbA1c, Lunge test, AGE and plantar fascia thickness were analysed in a logistic regression model. Higher plantar fascia thickness was significantly correlated with reduced vibration sensitivity, higher levels of HbA1c and AGEs, presence of diabetic retinopathy, and a worse diabetic foot risk classification. A significantly larger proportion of multiple daily insulin injections therapy (72% vs other therapies 41%, p<0.001) and self-monitoring blood glucose and flash glucose monitoring (73% vs continuous glucose monitoring 51%, p=0.007) was detected among patients with altered plantar fascia thickness. Conclusion: These findings indicate plantar fascia thickness showed a relationship between some diabetes complications and type of diabetes treatment. It could be a useful tool in T1DM management.