This paper presents an experimental and analytical study on the effect of elevated temperature on the short-term (up to 3 h) compression creep behaviour of polyethylene terephthalate (PET) foam, typically used in composite sandwich panels. Cubic PET specimens, with density of 99 kg/m3, were loaded in compression at various temperatures (from 20 ℃ to 140 ℃) under steady state conditions, for load levels of 10%, 20% and 30% of their residual compressive strength at each temperature. The results obtained show that for temperatures up to 140 ℃ the foam softens and degrades, resulting in significantly different compressive creep responses compared to that at room temperature (RT). At RT, compression creep was undetectable within the testing period. However, at 40 ℃ creep became noticeable, and at 60 ℃ a pronounced creep response was observed (at this temperature, the creep coefficient was the highest within the range of studied temperatures, ϕ ≈ 3). This shift in viscoelasticity was associated with the glass transition process (Tg = 65 ºC). The foam continued to show significant viscoelasticity for temperatures up to 140 ºC. For each temperature, linear viscoelasticity was observed with respect to the applied load. Based on the experimental data, Findley’s analytical power law was successfully calibrated. This law, originally developed for long-term creep at RT, provided a reasonable description of the short-term viscoelastic response of the PET foam under compression for temperatures up to 140 ºC.