A series of novel yellowish-orange emitting phosphors [Ca3-xMxSi2O7 (M = Eu2+)] have been synthesized by high temperature solid state reaction. The powder X-ray diffraction patterns reveals a single phase formation with excellent crystalline nature of the phases. Photoluminescence excitation and emission studies show that the Eu2+ doped phosphors show broad absorption (300-525 nm) and emits yellowish-orange-red spectral region. Further efforts have been made to tune the Eu2+ emission by crystal chemical isovalent substitution of Mg2+ in Ca2+ site. Compositionally induced phase transformation has been observed at y ≥ 0.25 in Ca2.985-yMgyEu0.015Si2O7. The yellowish-orange-red emission (y = 0) tuned to green color (y = 1) and the corresponding Commission Internationale de I'Eclairage (CIE) color coordinates (x, y) are changed from (0.5647, 0.4202) to (0.3540, 0.5932). © 2016 The Royal Society of Chemistry.