This paper focuses on a singular boundary value (SBV) problem of nonlinear fractional differential (NFD) equation defined as follows:
D
0
+
β
υ
τ
+
f
τ
,
υ
τ
=
0
,
τ
∈
0,1
,
υ
0
=
υ
′
0
=
υ
″
0
=
υ
″
1
=
0
, where
3
<
β
≤
4
,
D
0
+
β
is the standard Riemann–Liouville fractional (RLF) derivative. The nonlinear function
f
τ
,
υ
τ
might be singular on the spatial and temporal variables. This paper proves that a positive solution to the SBV problem exists and is unique, taking advantage of Green’s function through a fixed-point (FP) theory on cones and mixed monotone operators.