Objective: To evaluate the reliability and prevalence of enthesis ultrasound (US) elemental lesions in patients with psoriatic arthritis (PsA), using the Madrid Sonographic Enthesis Index (MASEI) and Outcome Measures in Rheumatology (OMERACT) definitions. Methods: The study included 27 PsA patients with metacarpophalangeal joint swelling. An US rheumatologist performed the MASEI examination. Prevalence and reliability of the included elemental lesions [structure, thickness, erosion, enthesophytes, power Doppler (PD), and bursae] were evaluated. In addition, three other PD definitions were checked: PD OMERACT (≤ 2 mm to the bone profile), PD enthesis–tendon (> 2 mm from the bone profile), and PD bursa. Short (3–5 s) videos of US examinations were recorded for reliability assessment. Results: MASEI and all PD definitions showed good to excellent reliability. The best reliability values were found in erosions, bursae, and PD. When present, the PD signal always appeared in more than one location of the evaluated areas. Enthesis Doppler was present in 81.5% of patients. Abnormal tendon structure and enthesophytes were the most prevalent lesions. Conclusion: MASEI demonstrates to be a reliable tool in PsA. All enthesis US Doppler definitions demonstrate to be reliable for its use in PsA with minimal differences, being PD MASEI the most sensitive in active patients.