We show that dual-wavelength-band (DWB) subwavelength grating couplers (SWGCs) can be designed for simultaneous coupling of the near-infrared and extended shortwave-infrared (SWIR) fundamental transverse electric polarized light at the same diffraction angle. Numerical simulations predict coupling efficiencies (CEs) larger than 34% for the DWB SWGCs operating in the S/C band (1.48/1.55 μm) and extended SWIR band (1.8-2.8 μm) with a widely and continuously tailorable peak wavelength separation between 250 and 1250 nm. The fabricated DWB SWGCs with peak wavelengths of (1.56, 2.255) μm and (1.487, 2.331) μm respectively obtain CEs of (20.2, 25.8)% and (20.6, 26.9)%, 1-dB bandwidths of 38 nm and 54 nm at a diffraction angle of 2°.