Two trials were conducted in this study investigating the possibilities of a seaweed extract from As-cophyllum nodosum (Maxicrop) in Japanese quails In the first trial, total 336 day old quaiifs were used. During 5 weeks, the animals fed diets containing 0, 0.01, 0.1 and 1 % extract. The effects of Maxicrop on body weight, daily gain, feed intake, feed efficiency, histologic changes in lymphoid tissues and some carcass parameters in quails were investigated. In the second trial, total 20 day old Japanase quails were divided 4 groups. Extract was added to basal diet at the levels of 0, 1,2 and 4 %, and whether its toxic effects were determined. The trial was lasted at 4 weeks. The results of this study were summarised as follows: Body weights and daily gains were not affected from of seaweed extract. In the group fed 1 % extract feed intake increased while feed efficiency decreased (P<0.05). No effect of extract on histological characteristics of lymphoid tissues and some carcass parameters was determined. It was found that seaweed extract up to 4 % in the diets of quails no pathological lesions.