Sulfated polysaccharides owe important space in therapeutics, since they exhibit promising biological activities. Their role in cancer alleviation was described in various literatures, but most of them failed to explain the molecular mechanism behind. In the present study, we determined the elemental composition, purity and molecular weight of sulfated polysaccharides, ESPs-CP, isolated and purified from the brown marine algae Padina tetrastromatica. The elemental analysis proved the presence of essential elements, UV visible spectroscopy revealed the absence of any impurities and GPC analysis showed the existence of both high and low molecular weight fractions in ESPs-CP. The anticancer potency of ESPs-CP was evaluated in Human cervical cancer cells, HeLa. IC50 value of ESPs-CP was 1.2 mg/ml and at this concentration, they could induce prominent apoptosis in the cells. There was also an obvious ROS generation and mitochondrial membrane depolarization imparted by ESPs-CP. The expression of genes in the apoptotic cascade such as p53, PUMA, PMAIP, BAX, BCL2, CASP9, CASP3 showed unique alterations in the presence of ESPs-CP. The results substantiated that the mechanism behind the anticancer effect of ESPs-CP is the induction of ROS mediated intrinsic pathway of apoptosis.