Abstract β-Phenylethylamine content was investigated in two green, five brown, and ten red marine algae by gas chromatography/mass spectrometry. β-Phenylethylamine was found in six red algae but was not detected in the brown and green algae studied. The highest amount of β-phenylethylamine was determined in Gelidium crinale (30.42 μg g -1 ). This is the first report of β-phenylethylamine in the algae tested and also the first to quantify β-phenylethylamine in marine algae.