[en] The aim of this paper is to study new holographic dark energy (HDE) model in modified $f(R,T)$ gravity theory within the framework of a flat Friedmann-Robertson-Walker model with bulk viscous matter content. It is thought that the negative pressure caused by the bulk viscosity can play the role of dark energy component, and drive the accelerating expansion of the universe. This is the motive of this paper to observe such phenomena with bulk viscosity. In the specific model $f(R,T)=R+\mathrm{\lambda <!--\; ??\; -->}T$, where $R$ is the Ricci scalar, $T$ the trace of the energy-momentum tensor and $\mathrm{\lambda <!--\; ??\; -->}$ is a constant, we find the solution for non-viscous and viscous new HDE models. We analyze new HDE model with constant bulk viscosity, $\mathrm{\zeta <!--\; ??\; -->}={\mathrm{\zeta <!--\; ??\; -->}}_0=\text{const.}$ to explain the present accelerated expansion of the universe. We classify all possible scenarios (deceleration, acceleration and their transition) with possible positive and negative ranges of $\mathrm{\lambda <!--\; ??\; -->}$ over the constraint on ${\mathrm{\zeta <!--\; ??\; -->}}_0$ to analyze the evolution of the universe. We obtain the solutions of scale factor and deceleration parameter, and discuss the evolution of the universe. We observe the future finite-time singularities of type I and III at a finite time under certain constraints on $\mathrm{\lambda <!--\; ??\; -->}$. We also investigate the statefinder and $\mathit{O}\mathit{m}$ diagnostics of the viscous new HDE model to discriminate with other existing dark energy models. In late time the viscous new HDE model approaches to $\mathrm{\Lambda <!--\; ??\; -->}\mathit{C}\mathit{D}\mathit{M}$ model. We also discuss the thermodynamics and entropy of the model and find that it satisfies the second law of thermodynamics.