<p>Dynamic vibration absorbers with grounded negative stiffness present inter-layer installation difficulties, which limits other usage options of these absorbers. To overcome this problem, a novel dynamic vibration absorber with ungrounded lever-type negative stiffness (LN-DVA) is proposed in this study, which makes the inter-layer installation possible and improve the control performance. First, based on the equations of motion, the displacement transfer function of the controlled primary structure is established. Then, the optimal parameters of the LN-DVA are determined by applying the fixed point theory (FPT) and numerical method, respectively, in order to minimize the resonant response and the results are analyzed. It is found that the lever ratio and the mass ratio influence the values of the optimal parameters. When the lever ratio increases, the primary structure displacement decreases in the resonance region and the good control performance is achieved. Furthermore, by evaluating the control performance for harmonic and random (earthquake ground motion) vibrations reduction of primary structure displacement, it is found that the proposed LN-DVA significantly outperforms the compared DVAs without negative stiffness. In particular, the LN-DVA outperforms the DVA with grounded negative stiffness. The obtained results are relevant because they provide more control performance and practical usage options of the proposed LN-DVA.</p>