Background <p>There is no consensus on the timing of postoperative radiotherapy for keloid.</p> Objective <p>We conducted this meta-analysis to investigate the appropriate time of radiotherapy for keloid in the first 24 hours after operation and identify the potential risk factors.</p> Materials and Method <p>A systematic review and meta-analysis were conducted on observational studies by searching PubMed, Embase, and the Cochrane Library. The pooled estimate of the keloid recurrence rate was calculated using a random-effects model. Subgroup analyses were conducted based on time, overtime, BED, length, and location of keloid.</p> Results <p>Eight observational studies with 507 keloids met the inclusion criteria, and 7 studies were finally included in this study after sensitivity analysis. The recurrence rate was lower in the 2 hours postoperative radiotherapy group (7% CI 2–14%) than in the 6 hours postoperative radiotherapy group (16%, CI 3–36%) (<i>P</i>&lt;0.01). In HDR subgroup analysis, the 2 hours group was better than the 6 hours group ((5%, CI 1–14%) versus (16%, CI 3–36.1%) (<i>P</i>&lt;0.01). Subgroup analysis based on BED indicated that the BED 30 group (5%, CI 1–14%) had a lower recurrence rate than the BED 20 group (6%, CI 0–21%) and the BED 15 group (26%, CI 19–33%) (<i>P</i>&lt;0.01). The keloid length &gt;5&#xa0;cm subgroup (10.4%, CI 0.4–29%) showed a higher recurrence rate than the keloid length &lt;5 cm group (9.9%, CI 0–41%) (<i>P</i>=0.011).</p> Conclusion <p>Immediate postoperative radiotherapy within 2 hours significantly decreased recurrence rate than postoperative radiotherapy within 6 hours.</p> Level of Evidence I <p>This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors &#xa0;<a href="http://www.springer.com/00266">www.springer.com/00266</a>.</p>