Motivated by the \((\mathfrak {g},K)\) -cohomology and Dirac cohomology, we determine Dirac series of \(\textrm{GL}(n,\mathbb {H})\) , and show that the spin lowest K-type of any Dirac series, which determines the Dirac cohomology, is unique and multiplicity-free for both \(\textrm{GL}(n,\mathbb {H})\) and \(\textrm{GL}(n,\mathbb {R})\) . This verifies a conjecture about uniqueness of the spin lowest K-type of Dirac series for \(\textrm{GL}(n,\mathbb {R})\) proposed by Dong and Wong (Int Math Res Not IMRN (12):10702–10735, 2022).