Introduction: Gynura crepioides (G. crepioides) belongs to the Asteraceae family and native to Southeast Asia, especially Indonesia. Gynura genuses are well known for their antioxidant properties. Hence, the current study aimed to study the effect of temperature on polyphenololic content and antioxidant properties on G. crepioides leaves extract. Methods: The extraction of G. crepioides leaves was carried out by Ultrasound-assisted extraction (UAE) method for 60 minutes by using ethanol (70 %) at three different temperatures 25°C and 50°C and 75°C. The total polyphenolic content (TPC) was investigated by using Folin-Ciocalteu assay, whereas the antioxidant potential (AOP) was determined by using phosphomolybdenum assay, and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Results: The results from the study showed that TPC of G. crepioides extracted at 25°C was significantly (p < 0.05) lower than 50°C and 75°C with 8.45 ± 0.31 mg GAE/g, 35.83 ± 1.22 mg GAE/g, 35.90 ± 0.78 mg GAE/g respectively. However, the results from AOP has demonstrated lower value of 70.62 ± 0.74 mg AAE/g at 75°C compare to 77.67 ± 0.26 mg AAE/g at 25°C and 81.53 ± 0.68 mg AAE/g at 50°C. From DPPH assay results revealed that extraction temperature at 50°C has EC50 (p < 0.05) lowest value of 92.64 ± 0.56 µg/mL compared to G. crepioides extracted at 25°C (98.50 ± 1.18 µg/mL) and 75°C (101.72 ± 9.09 µg/mL). An excellent correlation exhibited between TAC and DPPH radical scavenging assays with r = 0.95 and r2 = 0.89. Present study reveals that UAE method with 70% ethanol, 60 minutes extraction time at 50°C temperature is an optimum to extract highest phenolic content and antioxidants from G. crepioides leaves. Conclusion: It was concluded from the study that extraction temperature would affect the extraction of phytochemicals from plants in turn it affects the biological activities.