A field trial was conducted to assess the impact of organic manures (cattle and chicken manure) at rates of 2, 4 kg/plot (2m2) and seaweed extract concentrations (0, 2, 3 and 4 ml/l) on growth, yield and volatile oil constituents of fennel plants (Foeniculum vulgare Mill.) during the two successive seasons of 2020/2021 and 2021/2022. The chicken manure treatment at 4 kg/plot achieved the best results regarding all F. vulgare vegetative growth (except plant height), Fruit yield productivity and its constituents of the volatile oil. Foliar application treatment of seaweed extract in high concentration (4 ml/l) cleared significant impact on plant height, stem diameter, branch number/plant, umbel number/plant, fruit yield/plant, total fruit yield/feddan, volatile oil percentage, volatile oil yield per plant and per feddan during both seasons. Volatile oil samples of F. vulgare fruits collected from plants grown in soil amended with chicken manure at 4 kg/plot gave the highest percentage of anethole compound (39.13 %) and the lowest percentage of estragole compound (14.08%) in comparison with the other organic manure treatments as average of both seasons. The higher concentration of seaweed extract increased the percentage of anethole comparing with other concentrations. The foliar application by seaweed extract in high concentration on plants fertilized with chicken manure at the highest level seems to be the best interaction for getting higher yield and volatile oil of F. vulgare.