Thermal isolating service tubes and assemblies thereof for gas turbine engines are provided. The thermal isolating service tube comprises an inner tubular member defining a fluid passage and at least one outer tubular member disposed about the inner tubular member. A spacing volume is defined between at least the inner tubular member and an adjacent outer tubular member. The thermal isolating service tube comprises a unitary structure and has at least one portion with a curved configuration, a non-circular cross-sectional shape, or both.