Oxidation of n-pentanal is studied in a jet-stirred reactor at 10 atm for four dilute mixtures with equivalence ratios 0.3, 0.5, 1 and 2 and between 500–1150 K. A detailed kinetic sub-mechanism is developed and used along with the mechanisms representing the oxidation of two branched isomers of pentanal, namely 2- and 3-methylbutanal. At all conditions, n-pentanal showed a strong low-temperature reactivity and an NTC region. Among the experimentally observed species, ones related to the low-temperature oxidation of n-butyl radicals can be found, consolidating the importance of the (N-1) alkyl radicals in aldehyde chemistry. The kinetic mechanism showed good agreement against the data as well as other speciation data at atmospheric pressure from literature. The present data are also compared to previous similar studies on the oxidation of C3–C5 aldehydes in the same JSR and where n-pentanal shows the highest global reactivity.