We report on results pertinent to the room temperature first-order reversal curve (FORC) analysis of inverse Heusler alloy Fe2CoSi thin films with different thicknesses ( $t = 5$ , 10, 15, and 20 nm). Our analysis infers that magnetostatic interactions between magnetic grains enhance with an increase in the thickness of Fe2CoSi thin films. Indeed, such results are confirmed with the analysis of switching field distribution (SFD). Single domain (SD) to multi domain (MD) transformation is evidenced as the thickness increases from 5 to 20 nm. SD state is confirmed by symmetric contour around $B_{u} = 0$ axis, while, multidomain state is affirmed with no central peak and spreading of contour parallel to $B_{u} = 0$ axis. The change in domain state configuration for different thicknesses might strengthen the application of Fe2CoSi Heusler alloy films for the future spintronic applications. © 1965-2012 IEEE.