This work studied the impacts of betaine (Bet) supplementation on colostrum and milk quality of Aberdeen Angus cows and growth performance of their calves under New Valley, Egypt conditions. Twelve pregnant cows were assigned randomly into two equal groups (6 cows each). Treatments included: control (CG) and Bet group supplemented with 30 g Bet/h/d. Colostrum samples were collected within one hour after parturition at 1st day till 5th day postpartum. Then milk samples were collected biweekly till 14 weeks. The colostrum and milk samples were analyzed for chemical composition. Calves were placed next to their mothers for the first 5 days to ensure that they got enough colostrum. Birth weight was measured and recorded. Thereafter, body weight of calves was recorded at day 7, 14, 21, 56, 90 until the age of 105 day. Total gain and daily gain were calculated. The results showed a significant increase in milk yield and fat % in either colostrum or milk in the Bet group compared to the CG. Birth weight of calves in Bet-treated cows tended to be heavier at the birth than CG calves (35.60 vs. 34.43 kg). The Average daily gains were recorded for calves in Bet group (0.691 kg) compared with (0.675 kg) extent of CG. The Weaning weight was lower in CG (105.33kg) compared with Bet group (108.12 kg). The presented results concluded that Bet could enhance milk production and the growth performance of Aberdeen Angus during HS conditions of summer season.