Technical Abstract: The objective of this research was to examine the effects of feeding sericea lespedeza leaf meal [SL, Lespedeza cuneata (Dum.-Cours. G. Don)] on control of coccidiosis in lambs. In Exp. 1, naturally infected lambs (n = 76) were weaned (102.7 ± 1.4 d of age) in May (spring) and randomly assigned to receive 2% of BW/d of alfalfa pellets (control) or SL (n = 38/diet) with or without amprolium (n = 38/treatment) added to drinking water. Fecal oocyst (FOC), egg counts (FEC), and fecal score (1 = solid pellets; 5 = slurry) were determined every 7 d between weaning and 21 d post-weaning. In Exp. 2, twin rearing ewes were randomly assigned to two groups and their naturally infected lambs were fed a control creep supplement (16% CP; n = 40) or SL pellets (14% CP; n = 32) plus additional control diet to balance protein and energy 30 d before weaning. Intake of SL was initially low (100 g/lamb daily) and increased to 454 g/lamb daily after weaning (feeding of control lambs was matched to SL group). Lambs were weaned at 103.6 ± 0.9 d of age and moved to semi-confinement. The FEC, FOC, packed cell volume (PCV), fecal score, and dag score (soiling around rear of lamb; 1 = no soiling; 5 = heavy soiling) were determined at 14 d before weaning, weaning, 7, 14, and 21 d post-weaning. In Exp. 3, lambs were randomly assigned to a control or SL diet (n = 12/diet) fed at 1.4 kg/d for 22 d and inoculated with 50,000 sporulated oocysts on d 8, 11, and 13. The FEC, FOC, and fecal score were determined every 2 to 3 d between d 1 and 29 (d 0 = first day of dietary treatment). Data on all experiments were analyzed using mixed models. The FOC and FEC data were log transformed. Chi squared analysis was used to determine differences in incidence of treatment (sulfadimethoxine) for coccidiosis in Exp. 1 and 2. In Exp. 1, FOC and FEC were similar between dietary groups, and FOC declined more rapidly in amprolium treated lambs following weaning (P < 0.001). Fecal score was higher in the control compared with the SL fed lambs (P = 0.05), suggesting more signs of coccidiosis in control lambs. In Exp. 2, FOC was similar initially, but was reduced in SL fed lambs by weaning and remained lower thereafter (P = 0.004). Dag (P = 0.01)and fecal (P = 0.001) scores were similar before weaning, but lower in SL fed lambs by weaning and remained lower thereafter. No SL lambs required treatment for coccidiosis, whereas 33% of control lambs required treatment (P < 0.001). Fecal egg counts were similar before weaning, but were reduced in SL compared with control fed lambs after weaning (P < 0.001). In Exp. 3, FOC (P < 0.001) and FEC (P < 0.001) were reduced in SL compared with control fed lambs. Sericea lespedeza was effective in the prevention and control of coccidiosis as well as reducing GIN infection. Use of SL for treatment and prevention of coccidiosis could reduce lamb loss post-weaning, reduce the need to treat for coccidiosis, and create a significant economic benefit to livestock producers.