1. This research was conducted to determine the impact of diet supplementation with yeast cell walls and Yucca schidigera extract on the growth performance, antibody titres, and intestinal tissue histology of layer chicks.2. White, 1-d-old, Hy-Line hybrid chicks (n = 840) were divided into 4 main groups, each comprising 7 replicates of 30 chicks (n = 210): (1) control; (2) 1000 mg/kg yeast cell walls (YCW) added; (3) 1000 mg/kg Yucca schidigera extract (YE) added; and (4) 500 mg/kg YE + 500 mg/kg YCW added. The trial lasted 60 d.3. Daily weight gain of the chicks was positively affected between d 45-60 in the YE and YCW + YE groups compared with the control group.4. Overall, feed consumption did not differ between the control and YCW, YE, YCW + YE groups during the 60 d study period. Feed efficiency was better in the YE and YCW + YE groups than in the control group between d 1-60.5. During the 60 d evaluation period, live weight gain, and final live weight were higher in YE and YCW + YE groups than in the control group.6. Antibody titres against infectious bronchitis and infectious bursal disease did not differ among the 4 treatments, but those for Newcastle disease were higher in the YE + YCW groups than in the control, YCW and YE groups on d 45.7. There were differences in intestinal histomorphometry between the 4 treatments. The height of the jejunal and ileal villi was greater in the YE and YCW + YE groups than in the control and YCW groups8. It can be concluded that YCW and YE supplementation for layer chicks is beneficial for growth performance and intestinal histology during the 1-60 d growing period. © 2011 Taylor and Francis Group, LLC.