An unresolved, likely L dwarf companion to the DA white dwarf GD 1400 is reported. This would be only the second such system known, discovered 17 years after the prototype L dwarf, GD 165B, was determined to be a companion to a white dwarf. Photometric observations and model-predicted of the well-studied white dwarf primary stellar parameters indicate that GD 1400B has J - K 2.0 and MK = 12.13 mag. If correct, this would place GD 1400B at spectral type L6, and it would be the lowest-luminosity unevolved companion known to a white dwarf and thus a definite brown dwarf. However, a low-resolution Keck NIRSPEC 2.1–2.4 μm spectrum may not be consistent with known L dwarfs. Uncertainties in classification will remain until the binary is resolved or a trigonometric parallax is measured.
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