Running biomechanics and ethnicity can influence running economy (RE), which is a critical factor of running performance. Our aim was to compare RE of South East Asian (SEA) and non‑South East Asian (non‑SEA) runners at several endurance running speeds (10–14 km/h) matched for on‑road racing performance and sex. Secondly, we explored anthropometric characteristics and relationships between RE and anthropometric and biomechanical variables. SEA were 6% less economical (p = 0.04) than non‑SEA. SEA were lighter and shorter than non‑SEA, and had lower body mass indexes and leg lengths (p ≤ 0.01). In terms of biomechanics, a higher prevalence of forefoot strikers in SEA than non‑SEA was seen at each speed tested (p ≤ 0.04). Furthermore, SEA had a significantly higher step frequency (p = 0.02), shorter contact time (p = 0.04), smaller footstrike angle (p < 0.001), and less knee extension at toe‑off (p = 0.03) than non‑SEA. Amongst these variables, only mass was positively correlated to RE for both SEA (12 km/h) and non‑SEA (all speeds); step frequency, negatively correlated to RE for both SEA (10 km/h) and non‑SEA (12 km/h); and contact time, positively correlated to RE for SEA (12 km/h). Despite the observed anthropometric and biomechanical differences between cohorts, these data were limited in underpinning the observed RE differences at a group level. This exploratory study provides preliminary indications of potential differences between SEA and non‑SEA runners warranting further consideration. Altogether, these findings suggest caution when generalizing from non‑SEA running studies to SEA runners.