Two concentrated and well-characterized fucoidan-rich extracts were investigated to determine their benefits in topical applications. An Undaria pinnatifida extract, containing 85% fucoidan, and a Fucus vesiculosus co-extract, containing 60% fucoidan and 30% polyphenol, were assessed in a number of in vitro assays to measure the effect of the extracts on enzyme inhibition, glycation, antioxidant activity and Sirtuin 1 (SIRT1) protein expression. Double-blind, placebo-controlled clinical studies were also conducted to measure soothing, protection, wrinkle depth, brightness and skin spot intensity. Both extracts demonstrated marked inhibitory effects on processes linked to skin aging, including the increased expression of SIRT1 in vitro. Clinical testing established the efficacy of the extracts in a range of the tested applications, relative to placebo. The Fucus vesiculosus extract with high polyphenol content demonstrated additional in vitro antioxidant activity, as well as improved efficacy in skin brightening applications, relative to placebo. The major effects of the Undaria pinnatifida extract aided skin immunity, soothing and protection, while the Fucus vesiculosus extract most significantly affected age spot reduction and increased brightness, soothing and protection.