Abstract: While high-entropy magnetocaloric alloys offer exceptional compositional flexibility and stability for magnetic refrigeration, boosting their magnetic entropy change, working temperature range and refrigeration capacity concurrently remains challenging. Here, we show that microalloying GdTbDyHo with merely 0.4 at.% non-magnetic Y addresses this limitation. Our analysis indicates that Y uniformly dissolves in the hexagonal matrix lattice, disrupting 4f-4f exchange interactions and inducing local short-range order. This weakens antiferromagnetic coupling, accelerates the antiferromagnetic-to-ferromagnetic transition, and broadens its span. Consequently, the peak magnetic entropy change increases from 8.2 to 8.7 J kg⁻¹ K⁻¹, the working temperature range expands from 77 to 89 K, and the refrigeration capacity enhances by 25 % to 774 J kg⁻¹ (5 T) relative to the Y-free alloy, while the Néel temperature remains constant (~195 K). Our study establishes non-magnetic microalloying as a cost-effective, scalable strategy for designing high-performance magnetocaloric materials.