A new analytical method using curie-point pyrolyzer (CPP) and a gas chromatograph-flame ionization detector (GC-FID) system was developed. A suitable adsorbent (Carbopack X) has been applied for the first time on seawater and air samples to analyze biogenic isoprene and dimethyl sulfide (DMS). Target compounds from seawater samples (isoprene: 630 mL; DMS: 20 mL) and air samples (1 L) are adsorbed into a funnel-shaped glass adsorption tube at room temperature and then desorbed thermally (385 oC) using portable curie-point injector into gas chromatography-flame ionization detector (GC-FID). Good reproducibility (< 3%; < 1%), linearity (r2=0.999; r2=0.997) and low detection limits (0.5 pmol L-1; 0.07 nmol L-1) were obtained for seawater isoprene and DMS, respectively. In addition, this method can also be used for atmospheric isoprene quantitation, and is easier than the previous extraction technique. The CPP method was also applied for in situ seawater analysis in the coast of Zenibako in Hokkaido and Alaska. The results suggest that the CPP method can be used successfully at room temperature in place of the traditionally used cryo-trapping techniques in marine environments to determine dissolved trace isoprene and DMS in seawater.