A detailed understanding of the composition of lignocellulosic biomass-derived pyrolysis oils is essential in determining their storage stability before adopting a suitable upgrading strategy for their rational end use. The objective of the current study was to determine the effect of storage time and temperature on the chemical composition of pyrolysis oil derived from apricot or Prunus armeniaca seed residue (PASR). The pyrolysis oil was subjected to aging for 56 days at two storage temperatures (4 and 25 degrees C), and the samples were prepared and analyzed on 0, 7, 14, 28, and 56 days. The PASR pyrolysis was carried out in a'fixed bed pyrolysis reactor heated from ambient to 600 degrees C at a constant ramp rate of 5 degrees C min(-1) under an inert atmosphere. The aqueous and organic phases of pyrolysis oil were extracted with ethyl acetate and hexane, respectively, and characterized using gas chromatography mass spectrometry (GC- MS). The GC MS analysis showed a gradual change in pyrolysis oil composition with a pronounced decline in the'light oxygenates (acids, esters, aldehydes, ketones, etc.) and increase in the alcohols and heterocyclics. Remarkably, acids & esters were reduced from 11.9% to 1% in the organic phase, while alcohols & ethers increased from 19.3% to 27.5% in the aqueous phase at 25 degrees C. Heterocyclics, on the other hand, recorded an increase from 34.5% to 44.5% and 38.8% to 51.5%, respectively, in organic and aqueous phases at 25 degrees C. The observed changes were attributed to the notable aging reactions (such as polymerization of phenol with aldehyde, and hydrolysis of catechols). In contrast, the hydrocarbons remained relatively stable and showed an insignificant decrease during the studied storage period.