In this paper interval-valued fractional differential equations (IFDEs) under Caputo generalized Hukuhara differentiability are introduced. We present existence and uniqueness results for IFDEs with a Krasnoselskii–Krein-type condition. The solution to interval-valued fractional initial value problems under Caputo-type interval-valued fractional derivatives by a modified fractional Euler method (MFEM) and a modified Adams–Bashforth–Moulton method (MABMM) is also presented.