The　degradation　of　rubber　performance　in　service　environments　is　closely　associated　with　the　blooming　behavior　of　additives　in　the　rubber.　This　study　investigates　surface　precipitates　and　changes　in　tensile　properties　of　nitrile　butadiene　rubber　(NBR)　after　storage　at　85°C　in　air.　The　morphology,　elemental　composition,　phase　composition,　and　functional　groups　of　the　precipitates　were　analyzed　by　scanning　electron　microscopy,　energy　dispersion　spectroscopy,　X‐ray　diffraction,　and　fourier　transform　infrared　spectroscopy.　Based　on　the　morphology　of　internal　rubber　particles　and　precipitates　and　variations　in　the　Zn/C　mass　ratio　(ERZn),　the　reaction　between　zinc　oxide　and　stearic　acid　in　rubber　under　long‐term　thermal　environment　was　determined.　Four　stages　of　blooming　for　the　mixture　of　zinc　oxide　and　zinc　stearate　were　inferred,　and　the　impact　of　the　blooming　on　the　degradation　of　tensile　properties　of　NBR　was　established.　A　dramatic　decrease　in　the　elongation　at　break　(δk)　of　NBR　was　correlated　with　the　blooming　of　zinc　stearate　and　its　correspondingly　weakened　plasticizing　effect.HighlightsThe　core‐shell　structured　mixture　of　ZnO　and　Zn(St)2　bloomed　onto　the　surface　of　nitrile　butadiene　rubber.The　ratio　of　mass　percentages　of　Zn　to　C　evaluated　the　blooming　process　of　additives.The　migration　and　blooming　process　of　precipitates　were　divided　into　four　stages.The　decrease　in　elongation　of　the　rubber　was　attributed　to　the　blooming　of　Zn(St)2.