Background <p>The latissimus dorsi (LD) flap is a reliable option for breast reconstruction; however, its harvest may impair shoulder function. This study compared the latissimus dorsi flap with the muscle-sparing thoracodorsal artery perforator (TDAP) flap in terms of postoperative shoulder function. This study provides a comprehensive assessment of postoperative shoulder function using both patient-reported and objective clinician-based outcome measures.</p> Methods <p>A total of 43 patients who underwent partial breast reconstruction were included. Of these, 28 patients underwent reconstruction with the LD flap and 15 with the TDAP flap. Shoulder function was assessed 12 months postoperatively using the Shoulder Pain and Disability Index (SPADI), the Western Ontario Rotator Cuff Index (WORC), and the Constant-Murley Score (CMS). Patient demographic data, body mass index, smoking status, and comorbidities were recorded and analyzed statistically.</p> Results <p>SPADI scores were significantly lower in the TDAP flap group, indicating less pain and disability (total SPADI: 5.38% vs. 11.54%, <i>p</i> &lt; 0.001). WORC scores also favored the TDAP flap group (81 vs. 398.5, <i>p</i> &lt; 0.001), reflecting better quality of life. CMS scores were significantly higher in the TDAP flap group (80.0 vs. 64.5, <i>p</i> &lt; 0.001), with superior outcomes observed across all CMS subdomains, including pain, activities of daily living, range of motion, and strength. Consistent superiority across all three validated outcome measures was observed in the TDAP flap group.</p> Conclusions <p>The thoracodorsal artery perforator flap provides superior preservation of shoulder function compared to the latissimus dorsi flap. These findings support the concept of muscle-preserving reconstruction and suggest that this technique may be preferred in patients with high functional demands.</p> <p>Level of Evidence: Level II, risk / prognostic study.</p>