Let (M, g, J) be a closed Kähler manifold with negative sectional curvature and complex dimension m := dim C M ≥ 2. In this article, we study the unitary frame flow, that is, the restriction of the frame flow to the principal U(m)-bundle F C M of unitary frames. We show that if m ≥ 6 is even, and m = 28, there exists λ(m) ∈ (0, 1) such that if (M, g) has negative λ(m)-pinched holomorphic sectional curvature, then the unitary frame flow is ergodic and mixing. The constants λ(m) satisfy λ(6) = 0.9330..., lim m→+∞ λ(m) = 11 12 = 0.9166..., and m → λ(m) is decreasing. This extends to the even-dimensional case the results of Brin-Gromov [BG80] who proved ergodicity of the unitary frame flow on negatively-curved compact Kähler manifolds of odd complex dimension.