Background <p>The oncologic safety of laparoscopic-assisted surgery for synchronous colorectal cancer (SCRC), a distinct high-risk subgroup, remains under-investigated. This study aimed to compare the short-term and long-term outcomes of laparoscopic-assisted versus open surgery for SCRC.</p> Methods <p>A retrospective analysis of a cohort of 178 consecutive patients undergoing curative-intent surgery for SCRC between June 2007 and April 2019 was performed. To balance baseline covariates for the primary analysis, overlap weighting (OW) was applied to the cohort (133 laparoscopic, 45 open). A 1:1 propensity score matching (PSM) analysis was conducted as a sensitivity analysis. The primary outcomes were 5-year overall survival (OS) and 5-year disease-free survival (DFS).</p> Results <p>In the primary OW analysis, the laparoscopic group showed significantly less estimated blood loss (median, 100 mL vs. 200 mL; <i>P</i> = 0.003) and shorter time to first liquid diet (median, 4 vs. 5 days; <i>P</i> = 0.005) than the open surgery group. The two groups did not differ significantly in terms of 5-year OS (75.1% vs. 62.8%; <i>P</i> = 0.088) or 5-year DFS (65.69% vs. 59.3%; <i>P</i> = 0.110). Furthermore, in the multivariable Cox analysis, the laparoscopic approach was not an independent predictor of OS (adjusted HR, 0.61; 95% CI, 0.35–1.06) or DFS (adjusted HR, 0.70; 95% CI, 0.41–1.18). These findings were consistent in the PSM sensitivity analysis.</p> Conclusions <p>In this study, laparoscopic-assisted surgery for SCRC offered improved short-term outcomes while maintaining long-term oncologic safety.</p>