The high-quality growth of midwave infrared light emitters on silicon substrates will advance their incorporation into photonic integrated circuits, and also introduce manufacturing advantages over conventional devices grown on lattice-matched GaSb. Here we report interband cascade light emitting devices (ICLEDs) grown on 4 degree offcut silicon with 12% lattice mismatch. Four wafers produced functioning devices, with variations from wafer to wafer but uniform performance of devices from a given wafer. The full width at half maxima for the (004) GaSb rocking curves were as narrow as ∼ 163 arc seconds, and the root mean square surface roughness as small as 3.2 nm. Devices from the four wafers, as well as from a control structure grown to the same design on GaSb, were mounted epitaxial-side-up (epi-up). While core heating severely limited continuous wave (cw) emission from the control devices at relatively modest currents, efficient heat dissipation via the substrate allowed output from the devices on silicon to increase up to much higher currents. Although the devices on silicon had higher leakage currents, probably occurring primarily at dislocations resulting from the lattice-mismatched growth, accounting for differences in architecture the efficiency at high cw current was approximately 75% of that of our previous best-performing standard epi-down ICLEDs grown on GaSb. At 100 mA injection current, 200-µm-diameter mesas produced 184 µW of cw output power when operated at T = 25 °C, and 140 µW at 85°C. Epi-up mid-IR light emitters grown on silicon will be far simpler to process and much less expensive to manufacture than conventional devices grown on GaSb and mounted epi-down.