We used the brown alga Padina boryanawas to determine polyromantic hydrocarbons (PAHs) bioaccumulation at a Jeddah City seashore. We also measured PAHs in the coastal water and in algal tissues using gas chromatography mass spectrometry (GC-MS). Acenaphthene (Ace) and dibenzo(a,h)anthrancene (dB(a,h)An) were the main PAHs in sea water (50.02 and 46.18 ng l⁻¹, respectively) and in algal tissues (64.67 and 72.45ng g⁻¹, respectively), respectively. The ratios of low molecular weight/high molecular weight hydrocarbons (1.76-1.44), fluoranthene/pyrene (1.57-1.52), and phenanthrene/anthracene (0.86-0.67) in seawater and algal tissues indicated the origin of PAHs to be mainly pyrogenic. The high concentrations of PAHs in algal tissues demonstrated the utility of using Padina boryana as a biomonitor of PAH contamination and bioavailability in the coastal waters.