OBJECTIVE: To quantify changes in ductions following nasal transposition of the split lateral rectus muscle (NTSLR) for treating third nerve palsy. DESIGN: Retrospective cohort study. PARTICIPANTS: A single eye from each patient with third nerve palsy treated with NTSLR with ocular motility measurements. METHODS: Observation of changes in pre- and postoperative ductions. Outcome measures including patient demographic and surgical factors associated with the ability to adduct beyond the midline after NTSLR were evaluated using multivariable logistic regression. RESULTS: A total of 116 patients met the inclusion criteria for this study. The NTSLR significantly decreased abduction (median of 0 limitation [interquartile range (IQR), 0-0] prior to surgery to -4 [IQR, -4 to -3] after NTSLR; p < 0.001), with a corresponding improvement in adduction (median, -5 [IQR, -5 to -4] prior to surgery to -4 [IQR, -4 to -3] after NTSLR; p < 0.001). There was no change in median supraduction or infraduction after NRSLR (p > 0.05). The ability to adduct beyond the midline after NTSLR was demonstrated in 42% of patients. Although not statistically significant, a trend toward a postoperative ability to adduct beyond the midline was seen in patients who had concurrent superior oblique muscle tenotomy (odds ratio [OR] = 5.08; 95% CI, 0.91-40.9) or who were designated with partial rather than complete third nerve palsy (OR = 2.29; 95% CI, 0.82-6.70). CONCLUSIONS: NTSLR improves the horizontal midline positioning of eyes with third nerve palsy. Most eyes lose the ability to abduct, but some regain a modest ability to adduct while vertical ductions remain unchanged.