Quaternionic　Hilbert　spaces　play　an　important　role　in　applied　physical　sciences　especially　in　quantum　physics.　This　paper　addresses　the　frame　theory　in　quaternionic　Hilbert　spaces.　We　introduce　the　notion　of　approximately　dual　frames　in　quaternionic　Hilbert　spaces.　Then　we　characterize　(approximately)　dual　frames;　present　some　sufficient　conditions　for　constructing　other　(approximately)　dual　frame　pairs　from　one　(approximately)　dual　frame　pair;　and　obtain　some　stability　results　on　(approximately)　dual　frames.　©　2021,　Chinese　Academy　of　Sciences.　All　right　reserved.