We calculate the most interesting rare and CP-violating K and B decays in the Littlest Higgs model with T-parity. We give a collection of Feynman rules including v^2/f^2 contributions that are presented here for the first time and could turn out to be useful also for applications outside flavour physics. We adopt a model-independent parameterization of rare decays in terms of the gauge independent functions X_i,Y_i,Z_i (i=K,d,s), which is in particular useful for the study of the breaking of the universality between K, B_d and B_s systems through non-MFV interactions. Performing the calculation in the unitary and t Hooft-Feynman gauge, we find that the final result contains a divergence which signals some sensitivity to the ultraviolet completion of the theory. Including an estimate of this contribution, we calculate the branching ratios for the decays $K^+topi^+ ubar u$, $K_Ltopi^0 ubar u$, $B_{s,d}to mu^+mu^-$, $Bto X_{s,d} ubar u$, $K_L topi^0ell^+ell^-$ and $Bto X_{s,d}ell^+ell^-$, paying particular attention to non-MFV contributions present in the model. Imposing all available constraints we find that the decay rates for $B_{s,d} to mu^+ mu^-$ and $B to X_{s,d} u bar u$ can be enhanced by at most 50% and 35% relative to the SM values, while $Br(K^+topi^+ ubar u)$ and $Br(K_Ltopi^0 ubar u)$ can be both as high as $5 cdot 10^{-10}$. Significant enhancements of the decay rates $K_L topi^0ell^+ell^-$ are also possible. Simultaneously, the CP-asymmetries $S_{psi phi}$ and $A^s_text{SL}$ can be enhanced by an order of magnitude, while the electroweak penguin effects in $B to pi K$ turn out to be small, in agreement with the recent data.
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