We consider sign changes of Fourier coefficients of Hecke-Maass cusp forms for the group
S
L
3
(
Z
)
\mathrm {SL}_3(\mathbb Z)
. When the underlying form is self-dual, we show that there are
≫
ε
X
5
/
6
−
ε
\gg _\varepsilon X^{5/6-\varepsilon }
sign changes among the coefficients
{
A
(
m
,
1
)
}
m
≤
X
\{A(m,1)\}_{m\leq X}
and that there is a positive proportion of sign changes for many self-dual forms. Similar result concerning the positive proportion of sign changes also hold for the real-valued coefficients
A
(
m
,
m
)
A(m,m)
for generic
G
L
3
\mathrm {GL}_3
cusp forms, a result which is based on a new effective Sato-Tate type theorem for a family of
G
L
3
\mathrm {GL}_3
cusp forms we establish. In addition, non-vanishing of the Fourier coefficients is studied under the Ramanujan-Petersson conjecture.