The ternary nanofluids are considered due to their advantages in overcoming the stability drawback of mono and binary nanofluids. This study aims to heat transfer performance of Al2O3-TiO2-SiO2 ternary nanofluids in plain tube with wire coil under experimental. The ternary nanofluids were formulated using the composition ratio of 20:16:64 by volume in various volume concentrations ranging from 0.5 to 3.0%. Thermal conductivity and dynamic viscosity of ternary nanofluids were measured with KD2 Pro Thermal Properties Analyzer and Brookfield LVDV III Rheometer. Experimental forced convection heat transfer was carried out using a fabricated setup for Reynolds numbers from 2,300 to 12,000 at bulk temperature of 70 °C in plain tubes with wire coil inserts (0.83 ≤ P/D ≤ 2.50). Experimental results are highest thermal conductivity enhancement of 24.8% was obtained for ternary nanofluids at 3.0% volume concentration. The 3.0% volume concentration also shows the highest viscosity at all temperatures. The maximum heat transfer improvement for ternary nanofluids in a plain tube with wire coil (P/D-0.83), was attained by 3.0% volume concentration of up to 199.23%. The average TPF of the wire coil increases compared to the plain tube and improves further with volume concentrations in the range of 2.39 to 2.84.