The static method of isochoric saturation was used to measure the solubilities of CO2, O2 and N2 in rocket propellant 5 (RP5) at temperatures ranging from 253.15 to 323.15 K in 10 K intervals and pressures ranging from 0 to 120 kPa. The measurement accuracy of the constructed experimental setup was verified by measuring the solubility of CO2 in water. The relative expanded uncertainty (k = 2) in the solubility data was less than 4.0%. The solubilities of CO2, O2 and N2 in RP5 increased with pressure. As the temperature increased, the solubility decreased for CO2 solubility and increased for O2 and N2. Henry's constants for the three gases in RP5 decreased over the experimental temperature and pressure ranges in the order of N2 > O2 > CO2. The measured solubilities of CO2, O2 and N2 could be fitted with a modified Krichevsky–Kasarnovsky equation, and the maximum deviation between the measured and calculated data was less than 8.04%, 7.03% and 6.18%, respectively.