Experimental objectives were to evaluate the effects of supplementation with rumen-protected methionine (RPM) from 31 ± 2 to 127 ± 2 DIM (61 d after timed AI; TAI) on fertility and embryo development of dairy cows. Holstein cows (n = 309) were housed in a free-stall barn, milked twice daily, fed a basal diet formulated to 16.7% CP to deliver 2521 g of metabolizable protein (MP) with 6.93 lysine as % of MP and randomly assigned to once daily top-dressing with either (1) RPM, 21.2 g of Smartamine M mixed with 38.8 g of dry distillers grains (2.34 methionine as % of MP) or (2) Control (CON), 60 g of dry distillers grain (1.87 methionine as % of MP). All cows were synchronized using a Double Ovsynch protocol (GnRH-7d-PGF-3d-GnRH-7d-GnRH-7d-PGF-56h-GnRH-16h-TAI) to receive first TAI at 66 ± 3 DIM. Pregnancy diagnosis was done at 28 d (pregnancy-specific protein B) and at 32 and 61 d (ultrasound) after TAI. Embryo size and amniotic vesicle volume were determined by ultrasound on d 33 of pregnancy. Binomial data were analyzed by parity using Chi-squared or Fisher’s exact test. Continuous outcomes were analyzed by t-test or Wilcoxon sum-rank test. Only synchronized cows (92.1%, determined by progesterone concentrations) were used in the final analysis (n = 285). There was no effect of treatment on pregnancies per AI at 28 (65.5 vs. 66.7%; CON vs. RPM), 32 (58.6 vs. 61.4%), or 61 (54.4 vs. 58.3%) d after TAI. However, pregnancy loss was greater in multiparous cows for CON compared with RPM cows from 28 to 61 d (19.6 vs. 6.1%; P = 0.04) or from 32 to 61 d (8.9 vs. 0.0%, P = 0.03). However, there was no effect of treatment on pregnancy loss in primiparous cows (28 to 61 d, P = 0.50; 32 to 61 d, P = 0.50). Consistent with data on pregnancy loss, RPM increased embryonic size in multiparous cows (RPM vs. CON; amniotic vesicle volume, 592 vs. 472 mm³, P = 0.03; embryo abdominal diameter, 11.0 vs. 10.5 mm, P = 0.01; crown-rump length, 5.8 vs. 5.4 mm, P = 0.13), but had little effect on embryonic size in primiparous cows. Thus, top-dressing RPM increased embryo size and pregnancy maintenance in multiparous cows.