The determination of a space-dependent source term along with the solution for a 1-dimensional time fractional diffusion equation with nonlocal boundary conditions involving a parameter > 0 is considered. The fractional derivative is generalization of the Riemann-Liouville and Caputo fractional derivatives usually known as Hilfer fractional derivative. We proved existence and uniqueness results for the solution of the inverse problem while over-specified datum at 2 different time is given. The over-specified datum at 2 time allows us to avoid initial condition in terms of fractional integral associated with Hilfer fractional derivative. KEYWORDS bi-orthogonal system of functions, Hilfer fractional derivative, Mittag-Leffler function, nonlocal boundary conditions Math Meth Appl Sci. 2017;40:7737-7748.wileyonlinelibrary.com/journal/mma