  In this paper, we improve the sup-norm bound and the lower bound of the
number of nodal domains for dihedral Maass forms, which are a distinguished
sequence of Laplacian eigenfunctions on an arithmetic hyperbolic surface. More
specifically, let $\phi$ be a dihedral Maass form with spectral parameter
$t_\phi$, then we prove that $\|\phi\|_\infty \ll t_\phi^{3/8+\varepsilon}
\|\phi\|_2$, which is an improvement over the bound $t_\phi^{5/12+\varepsilon}
\|\phi\|_2$ given by Iwaniec and Sarnak. As a consequence, we get a better
lower bound for the number of nodal domains intersecting a fixed geodesic
segment under the Lindel\"{o}f Hypothesis. Unconditionally, we prove that the
number of nodal domains grows faster than $t_\phi^{1/8-\varepsilon}$ for any
$\varepsilon>0$ for almost all dihedral Maass forms.
