For　the　application　of　medium-entropy　alloys　(MEAs)　in　engineering,　high　cycle　fatigue　behavior　of　CoCrNi-based　MEAs　with　different　Al　and　Ti　additions　was　investigated　at　room　temperature　(RT)　and　350　degrees　C　in　this　study.　When　Al　and　Ti　contents　were　increased　from　1　to　4　at.%　and　2　to　3　at.%,　respectively,　yield　and　fatigue　strength　increased　by　70%　and　43%,　respectively,　hardness　and　ultimate　tensile　strength　increased　by　40%,　and　fracture　elongation　was　＞37%.　Between　RT　and　350　degrees　C,　the　effect　of　temperature　on　the　tensile　and　fatigue　strength　was　not　significant.　The　fatigue　crack　propagation　resistance　increased　with　increase　in　Al　and　Ti　contents.　Based　on　the　fatigue　strength　determined　in　the　study,　fatigue　life　prediction　equations　were　derived.　Microstructure　analysis　indicated　that　higher　tensile　and　fatigue　strength　were　attributed　to　uniformly　distributed　precipitates　of　nanoscale　L1(2)　particles　formed　in　the　FCC　matrix.