Bioactive ingredients derived from brown algae have been extensively used in the food, medicine, and cosmetic industries. In this study, fucoidans of low and high molecular fractions (LMF and HMF) extracted and isolated from brown alga Turbinaria decurrens were analyzed for their efficacy on seed germination, seedling growth, callus induction, direct organogenesis, and adventitious root formation in eggplant and finger millet. The yield and sugar content of LMF were higher than HMF. FTIR confirmed that the isolated fractions containing fucoidan has more sulfate groups in HMF than in LMF. The results showed an enhanced seed germination and seedling growth in both crops. In eggplant, 1 mg/L LMF treatment showed the maximum germination (91.6%), whereas, in finger millet, 0.1 and 0.5 mg/L LMF recorded a substantial increase in germination percentage (41.6 and 46%). Maximum fresh weight (FW) was noted with 1.0 mg/L LMF, and 1.0 mg/L LMF and 0.5 mg/L HMF showed maximum dry weight (DW) in eggplant. In finger millet, maximum DW was observed in 0.5 mg/L LMF and 1.0 mg/L HMF. Maximum biomass was noted in the 0.1 mg/L LMF treated group in the case of callus growth in eggplant. Similarly, the shoot tip initiation, proliferation, and plantlet regeneration were significantly improved with fucoidan LMF (0.1 mg/L). In conclusion, fucoidan extracted from T. decurrens exhibiting natural growth promoter property is reported for the first time in this study. These fucoidan fractions, LMF and HMF, can be utilized as cost-effective supplements in plant tissue culture media replacing the commercial PGRs for micropropagation.