<p>We investigated serial changes in intracranial artery dissection (ICAD) from the baseline to 12 months on vessel wall MRI. This prospective study enrolled 17 participants with clear onset of 20 unruptured ICADs between April 2016 and May 2018, and underwent vessel wall MRI within 1 week, and at 1-, 3-, 6-, and 12-months following symptom onset. Detection rates of imaging features, imaging time showing stable morphology and measurements were assessed, and compared between 1- and 3-month using exact McNemar’s and Wilcoxon signed-rank test. Detection rates of imaging features and quantitative measurements in 17 participants with 20 ICADs did not decrease from baseline to 1 month but decreased after 1-month (1 vs.3-months: dissecting flap [20/20 vs. 10/20, <i>P</i> = 0.002; 19/20 vs. 9/20, <i>P</i> = 0.002], double lumen [9/20 vs. 1/20, <i>P</i> = 0.008; 7/20 vs. 1/20; <i>P</i> = 0.031], intramural hematoma [18/20 vs. 9/20, <i>P</i> = 0.004; 17/20 vs. 9/20; <i>P</i> = 0.008], increased outer diameter [15/20 vs. 7/20, <i>P</i> = 0.008; 15/20 vs. 8/20, <i>P</i> = 0.016], normalized wall index [mean, 0.7 vs. 0.6, <i>P</i> = 0.008; 0.8 vs. 0.6, <i>P</i> &lt; 0.001], quantitative susceptibility mapping [mean, 0.5 vs. 0.3, <i>P</i> = 0.004; 0.4 vs. 0.2 ppm, <i>P</i> = 0.031], relative T1-weighted signal intensity [mean, 2.5 vs. 1.5, &lt; 0.001; 2.8 vs. 2.0, <i>P</i> = 0.007]). However, the decrease and stabilization did not occur in the progressive ICAD (<i>n</i> = 2). Stable morphology most frequently appeared at 3 months (8–9/18). Most of dissecting imaging features in ICAD were preserved within 1 month and resolved after 1 month following symptom onset, whereas progressive ICAD may not. Vessel wall MRI in ICAD is suggested to be performed within 1 month. If the dissecting imaging features persist or worsen after 3 months, further progression may be considered.</p><p><i>Trial registration</i> <a href="https://clinicaltrials.gov/">https://clinicaltrials.gov/</a>, NCT03213470.</p>