The thermal expansion coefficient (TEC) of single-layer graphene (SLG) was measured using temperature-dependent Raman spectroscopy in the range of 200 to 400 K. The TEC was found to be strongly temperature-dependent but remained negative throughout the entire temperature range, with a room temperature value of (−8.0 ± 0.7) × 10⁻⁶ K⁻¹. The strain caused by the mismatch between the TEC of graphene and its substrate plays a crucial role in determining the physical properties of graphene. The study highlights the importance of accounting for this strain effect when interpreting experimental data at cryogenic or elevated temperatures. The results show that the TEC of SLG is consistent with previous theoretical predictions and experimental measurements, but differ from a previous study that reported a negative-to-positive transition in the TEC at around 350 K. The findings emphasize the need for careful consideration of the TEC matching between graphene and the substrate to accurately determine the intrinsic physical properties of graphene over a wide temperature range.The thermal expansion coefficient (TEC) of single-layer graphene (SLG) was measured using temperature-dependent Raman spectroscopy in the range of 200 to 400 K. The TEC was found to be strongly temperature-dependent but remained negative throughout the entire temperature range, with a room temperature value of (−8.0 ± 0.7) × 10⁻⁶ K⁻¹. The strain caused by the mismatch between the TEC of graphene and its substrate plays a crucial role in determining the physical properties of graphene. The study highlights the importance of accounting for this strain effect when interpreting experimental data at cryogenic or elevated temperatures. The results show that the TEC of SLG is consistent with previous theoretical predictions and experimental measurements, but differ from a previous study that reported a negative-to-positive transition in the TEC at around 350 K. The findings emphasize the need for careful consideration of the TEC matching between graphene and the substrate to accurately determine the intrinsic physical properties of graphene over a wide temperature range.