Eight conducting polymer films of polypyrrole and its derivatives were used as sensitive and selective coatings for thickness-shear mode (TSM) acoustic wave sensors. They were applied to the detection of volatile alcohols and carbonyl compounds, which are important fish freshness determinants. The conducting polymers were synthesized and coated on TSM devices by electrochemical oxidation. The exposure of the coated TSM sensors to four compounds (pent-1-en-3-ol, oct-1-en-3-ol, nona-3,6-dien-1-ol and nona-2,6-dienal) was investigated, and a linear response with concentration found for the different aroma components. The sensor response was also found to be proportional to the film thickness. The response patterns obtained by grouping the data from the individual sensors are characteristic for each aroma molecule, and were investigated using both cluster and principal components analysis. The results demonstrate the feasibility of fish freshness determination through the use of a TSM sensor array combined with pattern recognition techniques.