Background: The effectiveness of methotrexate (MTX), a first-line treatment for localised scleroderma (morphea), has not been assessed using colour Doppler ultrasonography (CDU). Objectives: We aimed to ultrasonographically monitor disease activity in patients with morphea treated with MTX, assessing its effectiveness using an Ultrasound Morphea Activity Score (US-MAS). Materials & Methods: A retrospective cohort of 22 patients was studied between July 2014 and July 2019. The morphea of each patient, treated with MTX, was confirmed by histology and all patients had at least two CDU examinations. The US-MAS is based on published ultrasound signs of disease activity validated by histology. A weight-adjusted average MTX dose (mg/kg/wk) was used to standardize dosage, weight, and time between CDU examinations. The difference in US-MAS between two CDU examinations was determined. Statistical analyses included Wilcoxon and Fisher exact tests, the Spearman correlation coefficient, and risk ratios with 95% confidence intervals. To create two groups, we determined the median of the sample as the cut-off point for MTX dose (0.265 mg/kg/week). Significance was set at p≤0.05; Results: In all cases, CDU examinations showed subclinical signs of activity beyond the visible lesional borders, either in the same or adjacent corporal segments. A negative correlation was found between the change in US-MAS and MTX dose (Spearman coefficient,-0.45; p = 0.035). The group dosed at ≥0.265 mg/kg/wk showed a non-significant change in US-MAS (2-point decrease). No case became inactive. Conclusion: MTX is a treatment with a low effectiveness for morphea, causing only slight decreases in ultrasound activity at higher doses.