We conducted a retrospective comparative-effectiveness study of best-corrected visual acuity (BCVA) and refractive error (RE) after immediate sequential (ISBCS) and delayed sequential (DSBCS) bilateral cataract surgery. We tested 2 hypotheses: (1) among DSBCS patients, second-eye outcomes were no different than first-eye outcomes; (2) averaged between each patient’s 2 eyes, outcomes did not differ between ISBCS and DSBCS patients. Retrospective comparative-effectiveness study. Kaiser Permanente Northern California members who underwent noncomplex bilateral cataract surgery from January 1, 2013, through June 30, 2015. We performed an intention-to-treat analysis comparing ISBCS to DSBCS using conditional logistic regression analysis, accounting for surgeon and patient-level factors. BCVA, RE. The analysis of visual outcomes included both eyes of 13 711 DSBCS and 3561 ISBCS patients. Because of the large sample size, some statistical differences lacked clinical significance. Ocular comorbidities were slightly more prevalent in DSBCS patients. Postoperative BCVA was 20/20 or better in 48% of DSBCS first eyes, 49% of DSBCS second eyes, 53% of ISBCS right eyes, and 51% of ISBCS left eyes. The within-person difference in postoperative BCVA averaged zero (0.00) between the first and second DSBCS eyes, and between the ISBCS right and left eyes. After adjustment, average postoperative BCVA was better in ISBCS patients, although the difference was not statistically significant (compared with 20/20 or better: odds ratio for worse than 20/20 was 0.91, 95% confidence interval 0.83-1.01). Emmetropia (spherical equivalent -0.5 to 0 diopter) was achieved in 61% of first DSBCS eyes, 61% of second DSBCS eyes, 63% of ISBCS right eyes, and 63% of ISBCS left eyes. After adjustment, average postoperative RE was no different in ISBCS compared with DSBCS patients (compared with emmetropia: odds ratio for ametropia was 1.02, confidence interval 0.92-1.12). We confirmed 1 case of postoperative endophthalmitis in 10 494 ISBCS eyes (1.0 per 10 000 eyes) and 2 cases in 38 736 DSBCS eyes (0.5 per 10 000 eyes) (P = 0.6), and no patient had bilateral endophthalmitis. Compared with DSBCS, we found no evidence that ISBCS was associated with worse postoperative BCVA or RE, or with an increased complication risk.