In-plane magnetotransport properties of a EuFe 2 As 2 single crystal are investigated by angular-dependent magnetoresistance (MR) measurements. Strong anisotropy in magnetotransport properties is observed below the magnetic ordering temperature and it exhibits intimate correlations with the ordering states of both Eu 2+ and Fe 2+ spins as well as the twinned structure in EuFe 2 As 2 crystal. Such correlations lead to giant MR effect around the magnetic phase boundary, e.g., negative MR of ∼26% is observed at 5 K and 1 T upon the reorientation of Eu 2+ spins from antiferromagnetic to ferromagnetic configuration. Compared with Eu 2+ moments, Fe 2+ moments with antiferromagnetic arrangement generated relatively weak effect on MR due to its small ordered moment. All obtained MR results can be well understood based on the scenario of superzone boundary effect and the electron scattering by fluctuation of spins and twinning boundaries. It also suggests that the magnetic order state plays an important role for the determination of transport properties through the strong coupling between itinerant electrons and ordered spins.