Non-calcific supraspinatus tendinopathy (SNCCT) is a frequent cause of shoulder pain, often associated with functional impairment and reduced quality of life. Recent advancements in diagnostic imaging, including shear wave elastography (SWE), provide quantitative data on tendon stiffness and thickness, facilitating more precise evaluations. Extracorporeal shockwave therapy (ESWT) has emerged as a minimally invasive and effective treatment for SNCCT, but its effects on tendon properties measured through SWE require further investigation. This retrospective observational study aimed to evaluate the impact of ESWT on supraspinatus tendon characteristics in patients with SNCCT by assessing tendon thickness, SWE velocity, and clinical outcomes. Methods: This observational study enrolled 39 patients with SNCCT, aged 30-75 years, who received three ESWT sessions over 3 weeks. The intervention was delivered using a Modulith SLK system at an energy level of 0.20 mJ/mm with 2400 pulses per session. SWE and conventional ultrasound were used to measure tendon thickness and SWEv at baseline (T0) and 6 months post-treatment (T1). Clinical outcomes were assessed using the Visual Analog Scale (VAS), Constant and Murley Score (CMS), and modified Roles and Maudsley scale. Data were analyzed using paired -tests and correlation analyses. At baseline, affected tendons exhibited increased thickness (7.5 ± 0.9 mm) and reduced SWEv (3.1 ± 0.7 m/s) compared to healthy tendons (4.5 ± 0.7 mm and 6.9 ± 1 m/s, respectively; < 0.05). Six months after ESWT, tendon thickness decreased significantly (6.2 ± 0.9 mm, < 0.05), and SWEv increased (5.7 ± 1.8 m/s, < 0.05), indicating improved elasticity. Clinical outcomes improved significantly, with the VAS scores decreasing from 6.5 ± 1.4 to 3.2 ± 2.1, the CMS score rising from 59.1 ± 17.3 to 78.2 ± 17.7, and the modified Roles and Maudsley scale improving from 2.3 ± 0.6 to 1.5 ± 0.8 ( < 0.05 for all). SWEv positively correlated with the CMS (r = 0.4) and negatively with the VAS and the modified Roles and Maudsley scale (r = -0.6 and r = -0.5, respectively). ESWT significantly reduces tendon thickness and enhances elasticity, correlating with improvements in pain and functional scores. SWE proved to be a reliable method for monitoring structural and clinical changes in SNCCT. Further research, including randomized controlled trials, is recommended to confirm these findings and explore longer-term outcomes.