This study was conducted to estimate the effects of sire breed (Charollais, Dorper, Dorset, Hampshire, and Suffolk) and genetic group of the dam [local whiteface (Criolla), grade Hampshire, grade Suffolk, F(1) Dorper × Pelibuey, Australian composite, hair sheep (Barbados Blackbelly or Pelibuey), Dorset, Hampshire and Suffolk] on birth weight, survival rate from birth to weaning, and weaning weight adjusted to 65 d of age. Data were recorded from 2004 to 2006 on crossbreed lambs obtained by artificial insemination from 114 flocks in Central Mexico. High (above the mean) or low (below the mean) environmental categories were assigned to each record from flock-year-season effects solutions obtained in fixed-effects linear model analyses. Birth weights of lambs sired by Charollais rams (3.94 kg) were heavier (P < 0.05) than those sired by Suffolk (3.69 kg) whereas Dorper-, Dorset-, and Hampshire-sired lambs were intermediate. For weaning weight, lambs sired by Charollais were the heaviest (19.16 kg) compared with lambs sired by Hampshire (17.86 kg), Suffolk (17.79 kg), and Dorper (17.28 kg) whereas Dorset sired were the lightest (16.77 kg; P < 0.05). Lambs sired by Dorset rams had a lower survival rate (77.1%) than lambs sired by Charollais, Dorper, Hampshire, or Suffolk (81.6 to 83.3%; P < 0.05). Lambs from Australian composite, Dorset, Hampshire, and Suffolk dams were heavier for birth and weaning compared with lambs from local whiteface (Criolla), hair sheep breeds (Barbados Blackbelly or Pelibuey), or crosses (F(1) Pelibuey × Dorper) dams (P < 0.05) whereas lambs from grade Hampshire and grade Suffolk were intermediate. The genetic group of the dam had no effect (P > 0.05) on survival rate. Sire breed × environmental category interaction effect was significant for birth weight (P < 0.01) and weaning weight (P < 0.05), but relatively small changes on the ranking of sire breeds were observed between environmental categories for weaning weight. Genetic group of the dam × environmental category interaction effect was significant for birth and weaning weights (P < 0.01). Weaning weight of lambs from hair sheep breeds (Barbados Blackbelly or Pelibuey) and crosses (F(1) Pelibuey × Dorper) as well as purebred Dorset, Hampshire, and Suffolk dams were more affected when changing from the high to the low environmental category compared with the other genetic groups. No breed of the sire or genetic group of the dam × environmental category interactions were (P > 0.05) observed for survival rate.