In this paper, we report the detection of ejecta in the middle-aged Galactic supernova remnant G296.1−0.5 with the X-ray Imaging Spectrometer onboard the Suzaku satellite. The spectra of three lobes, north, south-east and south-west and interlobe regions, consist of soft (0.3–2.0 keV) emission originated from non-equilibrium ionization plasma. In north, south-east and interlobe regions, the thermal emission can be represented by a one-component non-equilibrium ionization (VNEI) model, in south-west region it can be represented by two-component VNEI model. The spectra of studied regions have lines of N, O, Ne, Mg and Si elements. Si emission from this remnant is shown for the first time in this work. Enhanced abundances of Ne, Mg and Si elements obtained show the ejecta contribution in all regions. Assuming that the remnant is in Sedov phase, we obtained ambient density n0∼ 0.45 cm−3, age t ∼ 2.8 × 104 yr, shock velocity Vs∼ 320 km s−1, shock temperature Ts∼ 1.2 × 106 K and swept-up mass Msw∼ 340 M⊙ at an adopted distance of d= 3 kpc.