The objective of the present study was to evaluate the effects of inbreeding on body weight at different ages in Moghani sheep. Traits included were birth weight (BW), 3-month weight (3MW), 6-month weight (6MW), 9-month weight (9MW), and yearling weight (YW). Data and pedigree information used in this study were collected at the Breeding Station of Moghani sheep, Iran during 1987-2005. All the animals were grouped into three classes according to the inbreeding coefficients obtained by their

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... gree: the first class included non-inbred animals (F=0 %); and the second and third classes included inbred animals (0<F≤0.10 and F>0.10, respectively). Average inbreeding rate was 2.93 % in the pedigree of Moghani sheep. The BW of animals within second class of inbreeding was significantly higher than those of lambs belonging to the third class (<i>P</i>&amp;lt;0.05). The 3MW of animals within third class of inbreeding was significantly (<i>P</i>&amp;lt;0.05) higher than those of lambs belonging to the first and second classes. The 6MW of animals within third class of inbreeding was significantly (<i>P</i>&amp;lt;0.05) lower than those of lambs belonging to the first and second classes. Animals within third class of inbreeding had greater mean of 9MW than two other groups (<i>P</i>&amp;lt;0.05). Also, the YW of animals within second class of inbreeding was significantly (<i>P</i>&amp;lt;0.05) lower than those of lambs belonging to the first and third classes. The utilization of designed mating system could be a suitable approach to maintain the level of inbreeding under control.