The development of a thresholdless laser operating above room temperature (RT) is key for the future replacement of electronics with photonic integrated circuits, enabling an increase of several orders of magnitude in computing speeds. Recently, thresholdless lasing characteristics at low temperature (4 K) have been demonstrated. However, for practical applications, RT laser emission becomes necessary. Here we report experimental evidence that is compatible with a laser based on InAsSb quantum dots embedded in a photonic-crystal microcavity that exhibits an ultralow-power threshold (860 nW) and high efficiency (β =0.85), thus operating in the near-thresholdless regime at RT in the 1.3 μm spectral window. The results open up a wide range of opportunities for RT applications of ultralow threshold lasers, such as integrated photonic circuitry or high sensitivity biosensors.