  Let $V$ be a $K$-vector space of dimension $n+1$. In this paper, we focus our
attention into the existence of irreducible homogeneous Ulrich bundles on flag
manifolds $\FF(p, q,n)$ which parameterizes all chains of linear subspaces
$L_{p} \subset L_{q} \subset \PP(V)$ of dimension $p< q$, respectively. We
determine all irreducible homogeneous Ulrich bundles on $\FF(0,n-1,n)$ and we
prove that there are exactly $2^{n-1}$. Similarly, we prove that $\FF(0,n-2,n)$
and $\FF(1,n-1,n)$ are also the support of irreducible homogeneous Ulrich
bundles. On the other hand, we prove that $\FF(0,1,n)$ do not support any
irreducible homogeneous Ulrich bundle. We end posing a conjecture concerning
the existence of irreducible homogeneous Ulrich bundles on $\FF(p,q,n)$ in
terms of $p$ and $q$.
