The encapsulation conditions of Eu2+‐doped calcium silicon nitride ((Ca0.90Eu0.10)2Si5N8) and strontium silicon nitride ((Sr0.98Eu0.02)2Si5N8) phosphors into phosphate glass ((50‐x)Na2O–xZnO–5B2O3–45P2O5; x = 10‐40) were examined by pressureless sintering (normal or infrared firing) and subsequent oxygen‐assisted hot isostatic pressing. The evaluation of water resistivity, as well as glass transition temperature (Tg), indicated that the excellent water resistivity and low Tg (313°C) could be achieved at x = 30. The colorless and clear glass body could be fabricated by infrared firing at 370°C for 20 minutes in air, followed by the hot isostatic pressing at 370°C for 24 hours (80%Ar + 20%O2, pressure: 130 MPa). The encapsulations of 3.0 mass% (Ca0.90Eu0.10)2Si5N8 and (Sr0.98Eu0.02)2Si5N8 into the glass body produced reddish orange light emission (peak wavelength: 604 nm under excitation wavelength of 423 nm) and red‐light emission (617 nm under 383 nm), respectively, showing higher chemical and thermal stability of nitride phosphors in the glass matrix.