The thermal decomposition of cyclopentene and cyclopentene+acetylene is studied in a shock-tube coupled to gas chromatography/mass spectrometry techniques under highly argon-diluted conditions with the goal of providing new experimental information about the polycyclic aromatic hydrocarbon (PAH) formation from cyclic C5 species. Experiments are carried out at a residence time of 4 ms, a pressure of 20 bar, and temperatures ranging from 940 to 1650 K. An ongoing detailed chemical kinetic model for PAH chemistry is updated to successfully capture the fuel decomposition, the formation of small hydrocarbons, and the concentration of the main PAH products. Cyclopentene mainly decomposes into linear pentadiene and cyclopentadiene. In all the datasets, small hydrocarbons mainly come from the consumption of pentadiene, and the channels leading to PAHs basically originate from reactions of cyclopentadienyl radical with cyclopentadiene, other cyclopentadienyl radical, propargyl, and indenyl. The comparison between experimental and simulated results data is overall satisfactory, but updates are still needed to better predict toluene, indene, and acenaphthylene measurements