The　working　fluid　of　the　hydrogen　recirculation　ejector　in　proton　exchange　membrane　fuel　cell　(PEMFC)　systems　is　humid　hydrogen　containing　water　vapour.　However,　previous　studies　on　the　hydrogen　recirculation　ejector　using　computational　fluid　dynamics　(CFD)　were　based　on　the　single-phase　flow　model　without　considering　the　phase　change　of　water　vapour.　In　this　study,　the　characteristics　of　the　phase　change　and　its　effect　on　the　ejector　performance　are　analysed　according　to　a　two-phase　CFD　model.　The　model　is　established　based　on　a　non-equilibrium　condensation　phase　change.　The　results　show　that　the　average　deviation　of　the　entrainment　ratio　predicted　by　a　single-phase　flow　model　is　25.8%　compared　with　experiments　involving　a　hydrogen　recirculation　ejector,　which　is　higher　than　the　15.1%　predicted　by　the　two-phase　flow　model.　It　can　be　determined　that　droplet　nucleation　occurs　at　the　junction　of　the　primary　and　secondary　flow,　with　the　maximum　nucleation　rate　reaching　4.0　×　1020　m−3s−1　at　a　primary　flow　pressure　of　5.0　bar.　The　higher　temperature,　lower　velocity,　and　higher　pressure　of　the　gas　phase　can　be　found　in　the　mixing　region　due　to　condensation,　resulting　in　a　lower　entrainment　performance.　The　nucleation　rate,　droplet　number,　and　liquid　mass　fraction　increase　remarkably　with　an　increasing　primary　flow　pressure.　This　study　provides　a　meaningful　reference　for　understanding　phase　change　characteristics　and　two-phase　flow　behaviour　in　hydrogen　recirculation　ejectors　for　PEMFC　systems.　©　2021　Hydrogen　Energy　Publications　LLC