We study the limit cycles of the fifth-order differential equation
x
⋅
⋅
⋅
⋅
⋅
−
e
x
⃜
−
d
x
⃛
−
c
x
¨
−
b
x
˙
−
a
x
=
ε
F
x
,
x
˙
,
x
¨
,
x
⋯
,
x
⃜
with
a
=
λ
μ
δ
,
b
=
−
λ
μ
+
λ
δ
+
μ
δ
,
c
=
λ
+
μ
+
δ
+
λ
μ
δ
,
d
=
−
1
+
λ
μ
+
λ
δ
+
μ
δ
,
e
=
λ
+
μ
+
δ
,
where
ε
is a small enough real parameter,
λ
,
μ
, and
δ
are real parameters, and
F
∈
C
2
is a nonlinear function. Using the averaging theory of first order, we provide sufficient conditions for the existence of limit cycles of this equation.