The aim of this study was to evaluate the effect of replacing two levels (20 or 40%) of chemically or biologically treated castor meal (CTCM or BTCM) of the control diet soybean meal on growing rabbits performance. One hundred New Zealand White rabbits, six weeks old with an average live body weight ranging from 733 to 777g were randomly divided into five groups and each group was divided into 5 replicated (4 rabbits/replicate). The growing period lasted 8 weeks. Diets were offered ad-libtium and fresh water was available all times. Results indicated that chemical and biological treatments were somewhat affect chemical composition in which mainly CP content was markedly increased but CF was decreased by biological treatment. Nutrients digestibility data indicated that insignificant differences among dietary treatments in respect of DM and OM digestibilities. Digestibility of CF, EE, NFE and CP were significantly decreased by using diet containing 40% BTCM in comparison with control. The values of DCP and TDN were significant lower with 40% BTCM diet than those of control one, while the other tested diets mostly didn't differ significantly than control regarding these parameters. Nitrogen balance values were insignificant decreased for diets containing CTCM and BTCM at levels 20 and 40% compared with control diet. Final body weight and body weight gain values were insignificant decreased for rabbits fed all diets except for those fed on 40% BTCM diet that they values were decreased significantly compared with those of control one. Feed intake recorded the lowest value with rabbits fed 20% CTCM diet, while the highest value was occurred with those fed on 40% CTCM diet. Based on control diet most tested diets didn't affect significantly feed intake. The best FCR was occurred with 20% CTCM sit, while worst one was associated with 40% CTCM diet and difference among most treatments non-significant. There were no significant differences among treatments regarding the most blood constituents and all values were in the normal range. Diets contained CTCM or BTCM at 20% level were achieved the highest economic efficiency followed by control diet or 40% BTCM diet and the least one was associated with 40% CTCM diet. Generally, it could be recommended to use the CTCM or BTCM in growing rabbit's diets at 20% instead of soybean meal without any adverse effects on their growth performance and health condition.