Let K 0 (V/X) be the relative Grothendieck group of varieties over X ∈ Obj(V), with V = V (qp) k (resp. V = V an c ) the category of (quasi-projective) algebraic (resp. compact complex analytic) varieties over a base field k. Then we constructed the motivic Hirzebruch class transformation Ty * : K 0 (V/X) → H * (X) ⊗ Q[y] in the algebraic context for k of characteristic zero, with H * (X) = CH * (X) (resp. in the complex algebraic or analytic context, with H * (X) = H BM 2 * (X)). It "unifies" the wellknown three characteristic class transformations of singular varieties: MacPherson's Chern class, Baum-Fulton-MacPherson's Todd class and the L-class of Goresky-MacPherson and Cappell-Shaneson. In this paper we construct a bivariant relative Grothendieck groupin the algebraic context with k of characteristic zero (resp., complex analytic context).We also construct in the algebraic context (in any characteristic) two Grothendieck transformations mCy = Λ mot y :with K alg (f ) the bivariant algebraic Ktheory of f -perfect complexes and H the bivariant operational Chow groups (or the even degree bivariant homology in case k = C). Evaluating at y = 0, we get a "motivic" lift T 0 of Fulton-MacPherson's bivariant Riemann-Roch transformation τ : K alg → H ⊗ Q. The covariant transformations mCy : K 0 (V qp /X → pt) → G 0 (X) ⊗ Z[y] and Ty * : K 0 (V qp /X → pt) → H * (X) ⊗ Q[y] agree for k of characteristic zero with our motivic Chern-and Hirzebruch class transformations defined on K 0 (V qp /X). Finally, evaluating at y = −1, for k of characteristic zero we get a "motivic" lift T −1 of Ernström-Yokura's bivariant Chern class transformation γ :F → CH.