This study examined the effects of seaweed extract and some plant growth regulators (GA₃) on dahlia during the two successive seasons (2021/2022 and 2022/2023). The experiment was conducted at the Ornamental Department of El Gemaeza Agricultural Research Station, Agric. Res. Center, El-Ghrbia Governorate, Egypt under open-field conditions in sunlight during the two seasons. Experiment with a completely randomized block design with five replicates for 15 treatments i.e., control, three levels of seaweed extracts (SWE) at 500, 1000, and 1500 mg/l, three levels of GA₃ (50, 100 and 150 mg/l), three levels of CPPU (50, 100 and 150 mg/l) and combinations of 500 mg/l SWE + 50 mg/l CPPU + 50 mg/l GA₃, 1000 mg/l SWE + 100 mg/l CPPU + 100 mg/l GA₃, 1500 mg/l SWE + 150 mg/l CPPU + 150 mg/l GA₃, 500 mg/l SWE + 100 mg/l CPPU + 150 mg/l GA₃ and 1500 mg/l SWE + 100 mg/l CPPU + 50 mg/l GA₃. Plant height, stem diameter, number of branches per plant, fresh and dry weights of shoots, total chlorophyll, and leaf area index were the vegetative growth parameters, while the flowering characters were flower length, flower diameter, stalk length, fresh and dry weights of flowers, number of flowers per plant, and number of days to flower, days of flower longevity and vase life. The results demonstrated that when compared to the control treatment (which was left untreated during both seasons), SWE at 1500 mg/l + CPPU at 150 mg/l + GA₃ at 150 mg/l recorded higher values for all vegetative growth and flowering characteristics