Diabetic foot ulcers (DFUs) are a very common cause of mortality and morbidity. The distinction between infected and non-infected DFU remains a very challenging task for clinicians in everyday practice. Even when infection is documented, the spectrum of diabetic foot infection is wide, ranging from cellulitis and soft tissue infection to osteomyelitis. Procalcitonin (PCT), a well-established sepsis biomarker, has been used in the diagnosis of several infections including osteomyelitis in patients with diabetes mellitus. This review gathers and presents all the relevant data, up until now, regarding the use of PCT as an assessment tool in diabetic patients with foot infection. Current evidence suggests that PCT levels could aid clinicians in distinguishing infected from non-infected DFUs as well as in the distinction between soft tissue infection and bone involvement, but further and larger studies are warranted to confirm these findings.