The continuous rise in the cost of refined asphalt binders has increased the need for alternative road materials. Natural sand–asphalt mixtures, which have been already used in the construction of flexible pavements, constitute a promising non-standard asphalt material. Unfortunately, most of these mixtures have not been fully characterised or have been characterised using techniques that are unable to predict their performance. This paper proposes the application of the dynamic mechanical analyser (DMA) test to determine viscoelastic material properties of natural asphalt mixtures. The technique is also recommended to evaluate the mechanical deterioration of these materials and the impact of relevant construction factors, such as a compaction temperature, on their mechanical performance. Experimental results of applying DMA testing on a natural sand–asphalt mixture corroborated that this method provides reliable information to support decision-making processes regarding the responsible use of these mixtures in road infrastructure projects.