Abstract-Compsopogon helwanii is a new Egyptian species of the genus compsopogon, collected (in 1999) from Ain Helwan Spring. It dominated all over the year. Neither this new red alga species, nor the other known eight compsopogon species were subjected to any physiological or biochemical studies. This is the first investigation concerning the biological activities of this new algal species. Methanolic extract of this alga was tested for antimicrobial (G+ve, G-ve bacteria, yeast, fungi), antialgal (green and cyanobacteria) , antioxidant (DPPH and ABTS assays) and anticancer (EACC) activities. The obtained results correlated the biological activities to the contents of phycobilin pigments, spermine derivatives (GC/MS) and other active constituents in this algal extract.