An apparatus for hydrocarbon resource recovery from a subterranean formation includes a radio frequency (RF) source, an RF antenna to be positioned within the subterranean formation to deliver RF power to the hydrocarbon resource within the subterranean formation, and an RF transmission line extending between the RF source and the RF antenna. The RF transmission line may include RF transmission line sections coupled together in end-to-end relation. Each section may include an inner conductor, an outer conductor surrounding the inner conductor, and an outer load-carrying tubular member surrounding the outer conductor. A respective coupling assembly joins ends of adjacent sections together. Each coupling assembly may include an electrical coupler being fixedly connected to first ends of corresponding inner and outer conductors and being slidably connected to opposing second ends of adjacent inner and outer conductors, and a mechanical coupler connecting ends of adjacent load-bearing tubular members together.