We study the invisible decay of the Higgs boson into a pair of stable, heavy photons, H → AH AH, in the littlest Higgs model with T-parity. For a symmetry breaking scale of f = 450 GeV, the branching ratio H → AH AH can be as high as 93% for Higgs masses below 150 GeV. For f = 500 GeV, the invisible branching ratio is about 75% in the Higgs mass range 135 - 150 GeV and 10 (5.5) % for mH = 200 (600) GeV. It drops to a few percent for f larger than 600 GeV. We have found regions in parameter space, allowed by the electroweak precision data, with such low values of f for 115 GeV < mH < 650 GeV. © 2007 Elsevier B.V. All rights reserved.