A systematic study of the influence of oxygen partial pressure on 110 K phase formation in the Bi‐Pb‐Sr‐Ca‐Cu‐O system has been undertaken on the optimum nominal composition to promote the Bi2Sr2Ca2Cu3Ow(2223, 110 K) phase, i.e.; Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Ow. The relationship between 110 K phase fraction, oxygen partial pressure, sintering temperature, and time has been mapped for this composition via experimental data. The optimum conditions for 110 K phase formation were identified as 0.01≤PO2≤0.35 atm, at 820≤T≤880 °C for ≤36 h with intermediate grinding every 6 h. The single 110 K phase stability range was determined asPO2≤0.5 atm. The variation of oxygen partial pressure during the 110 K phase formation process was monitored via a Y2O3‐ZrO2oxygen sensor and a possible mechanism for its formation and the effect ofPO2thereon is discussed.