Very high energy (VHE; E > or =, slanted E 100 GeV) and high-energy (HE; 100 MeV < or =, slanted E < or =, slanted 100 GeV) data from gamma-ray observations performed with the H.E.S.S. telescope array and the Fermi-LAT instrument, respectively, are analyzed in order to investigate the non-thermal processes in the starburst galaxy NGC 253. A power-law fit to the differential HE gamma-ray spectrum reveals a photon index of Gamma = 2.24 + or - 0.14 sub(stat) + or - 0.03 sub(sys) and an integral flux between 200 MeV and 200 GeV of F(0.2-200 GeV) = (4.9 + or - 1.0 sub(stat) + or - 0.3 sub(sys)) x 10 super(-9) cm super(-2) s super(-1). No evidence for a spectral break or turnover is found over the dynamic range of both the LAT instrument and the H.E.S.S. experiment: a combined fit of a power law to the HE and VHE gamma-ray data results in a differential photon index Gamma = 2.34 + or - 0.03 with a p-value of 30%..