The aims of the study were to investigate the importance of maternal effects and to determine the most appropriate model of analyses for pre- and post-weaning daily gain of Turkish Merino lambs. Genetic parameters were estimated by REML procedure using DFREML program. Twelve different animal models were fitted by including or excluding maternal genetic effect. maternal permanent environmental effect, maternal temporary environmental effect and covariance between direct-maternal genetic effects. On the basis of log likelihood ratio test results, Model 2b, which included direct genetic and maternal temporary environmental effects, was determined to be the most appropriate model for both traits. The maternal temporary environmental effect was the most important source of variation for both traits. This effect contributed about 35% and 14% to the phenotypic variance for pre- and post- weaning daily gain, respectively. The maternal genetic and permanent environmental effects were important for only pre-weaning average daily gain. Depending on the model, the estimates of maternal heritability ranged from 0.005 to 0.082 and from 0.010 to 0.027 for pre- and post-weaning daily gain.