Beliau dibai'ah sebagai khalifah tiga malam selepas pengebumian 'Umar. Diriwayatkan bahawa dalam tempoh hari-hari itu orang ramai berkumpul bersama 'Abdur-Rahman bin 'Auf, menasihatinya dan berbicara secara rahsia dengannya. Tidak seorang pun yang berakal yang duduk bersendirian dengannya melihat sesiapa yang setara dengan 'Uthman. Apabila 'Abdur-Rahman duduk untuk memberi bai'ah, beliau memuji Allah dan berkata dalam ucapannya, "Saya melihat bahawa orang ramai menolak sesiapa pun selain 'Uthman." Ibnu 'Asakir meriwayatkannya daripada al-Miswar bin Makhramah. Dalam riwayat lain, "Sekarang! 'Ali, saya telah menyelidiki di kalangan orang ramai dan saya tidak melihat mereka mengutamakan sesiapa yang setara dengan 'Uthman. Oleh itu, janganlah engkau membuka jalan untuk menentang dirimu sendiri." Beliau memegang tangan 'Uthman dan berkata, "Kami membai'ahmu menurut Sunnah Allah, Sunnah Rasul-Nya dan Sunnah dua khalifah selepas beliau." 'Abdur-Rahman membai'ah beliau, dan kaum Muhajirin serta kaum Ansar turut membai'ah beliau.

He was pledged allegiance as khalifah three nights after the burial of cUmar. It is related that people got together, during those days, with cAbd ar-Rahman ibn cAwf, advising him and talking confidentially with him. Not one person of judgement who sat alone with him saw any to equal cUthman. When cAbd ar-Rahman sat to pledge allegiance, he praised Allah and said, during his speech, ‘I saw that people refuse anybody but cUthman.’ Ibn cAsakir narrated it from al-Miswar ibn Makhramah. In another narration, ‘Now! cAli, I have researched among people and I don’t see them regarding anyone equal to cUthman. Therefore, do not make a way against yourself.’ He took the hand of cUthman and said, ‘We pledge allegiance to you according to the Sunnah of Allah, the Sunnah of His Messenger and the Sunnah of the two khalifahs after him.’ cAbd ar-Rahman pledged allegiance to him and the Muhajirun and the Ansar pledged allegiance to him.

Ibn Sa'd meriwayatkan bahawa Anas berkata: 'Umar memanggil Abu Talhah al-Ansari satu jam sebelum beliau wafat dan berkata, "Engkau termasuk dalam lima puluh orang dari kalangan Ansar bersama kumpulan ini, iaitu para sahabat syura, kerana mereka, menurut pendapatku, akan berkumpul di sebuah rumah. Berdirilah di pintu itu bersama sahabat-sahabatmu, jangan biarkan sesiapa masuk, dan jangan biarkan hari ketiga berlalu tanpa mereka melantik salah seorang daripada mereka sebagai ketua." Dalam Musnad Ahmad terdapat riwayat bahawa Abu Wa'il berkata: Aku bertanya kepada 'Abd al-Rahman bin 'Awf, "Bagaimana engkau boleh membai'ah 'Uthman dan mengabaikan 'Ali?" Beliau menjawab, "Di manakah kesalahanku? Aku memulakan dengan 'Ali dan aku berkata, 'Adakah aku harus membai'ahmu mengikut Kitab Allah, Sunnah Rasul-Nya dan amalan Abu Bakar dan 'Umar?' Beliau berkata, 'Dalam apa yang aku mampu.' Kemudian aku menawarkan perkara yang sama kepada 'Uthman dan beliau berkata, 'Ya.'" Diriwayatkan bahawa 'Abd al-Rahman berkata kepada 'Uthman secara bersendirian, "Jika aku tidak membai'ahmu, siapakah yang engkau tunjukkan kepadaku?" Beliau menjawab, "'Ali." Beliau berkata kepada 'Ali, "Jika aku tidak membai'ahmu, siapakah yang engkau tunjukkan kepadaku?" Beliau menjawab, "'Uthman." Kemudian beliau memanggil az-Zubayr dan berkata, "Jika aku tidak membai'ahmu, siapakah yang engkau tunjukkan kepadaku?" Beliau menjawab, "'Ali atau 'Uthman." Kemudian beliau memanggil Sa'd dan berkata, "Siapakah yang engkau tunjukkan kepadaku?"

Ibn Sacd narrated that Anas said: cUmar sent for Abu Talhah al- Ansari an hour before he died and said, ‘You be among fifty of the Ansar along with this group, the companions of the counsel, because they, as I believe, will gather in a house. Stand at that door with your companions, allow no-one to enter, and do not leave them to allow the third day to pass without their appointing one of themselves to the command.’ There is in the Musnad of Ahmad that Abu Wa’il said: I said to cAbd ar-Rahman ibn cAwf, ‘How could you have sworn allegiance to cUthman and neglected cAli?’ He said, ‘Where was my wrong action? I started with cAli and I said, “Shall I swear allegiance to you according to the Book of Allah, the Sunnah of His Messenger and the conduct of Abu Bakr and cUmar?” He said, “In what I am able.” I hen later I offered the same to cUthman and he said, “Yes.”’ It has been related that cAbd ar-Rahman said to cUthman in private, ‘If I don’t pledge allegiance to you who would you point out to me?’ He said, ‘cAli.’ He said to cAli, ‘If I don’t pledge allegiance to you who would you point out to me?’ He said, ‘cUthman.’ Then he called for az-Zubayr and said, ‘If I don’t pledge allegiance to you who would you point out to me?’ He said, ‘cAli or cUthman.’ Then later he called for Sacd and said, ‘Whom would you indicate to me?

"kerana, adapun saya dan kamu, kami tidak menginginkannya." Dia berkata, "'Uthman." Kemudian cAbd ar-Rahman meminta nasihat semua tokoh terkemuka dan mendapati bahawa kebanyakan mereka cenderung kepada 'Uthman.

because, as for me and you, we don’t want it.’ He said, ‘'Uthman.’ Then cAbd ar-Rahman sought the counsel of all the notables and saw that most of them were inclined to cUthman.

Ibn Sa'd dan al-Hakim meriwayatkan bahawa Ibn Mas'ud, semoga Allah meredhainya, berkata, ketika 'Uthman dibai'atkan, "Kami telah menyerahkan urusan kepada yang terbaik di kalangan mereka yang tinggal, dan kami tidak lalai." Pada tahun pemerintahannya ini, Rayy dibuka [untuk Islam]. Ia pernah dibuka sebelum ini kemudian hilang. Pada tahun itu banyak orang mengalami mimisan, sehingga tahun itu dikenali sebagai "Tahun Mimisan." 'Uthman sendiri diserang mimisan sehingga beliau tidak dapat menunaikan haji dan melantik seseorang untuk menggantikannya. Pada tahun itu banyak kubu Byzantine dapat ditawan. Pada tahun itu juga 'Uthman melantik Sa'd ibn Abi Waqqas sebagai gabenor Kufah dan memberhentikan al-Mughirah.

Ibn Sacd and al-Hakim narrated that Ibn Mascud, may Allah be pleased with him, said, when cUthman was pledged allegiance, ‘We have charged with command the best of those remaining and we have not been negligent.’ In this year of his khilafah, Rayy was opened [to Islam], and it had been opened previously and subsequently lost. In that year many nosebleeds occurred among people, so that it was known as, ‘The year of the nosebleeds.’ cUthman was afflicted by nosebleeds to such an extent that he stayed away from the Hajj and deputed someone in his place. In that year many Byzantine fortresses were taken. In it cUthman appointed Sacd ibn Abi Waqqas as governor of Kufa and removed al-Mughirah.

فِي سَنَةِ 25 هـ، عَزَلَ عُثْمَانُ سَعْدًا عَنِ الْكُوفَةِ، وَوَلَّى الْوَلِيدَ بْنَ عُقْبَةَ بْنِ أَبِي مُعَيْطٍ، وَكَانَ صَحَابِيًّا، وَأَخًا لِعُثْمَانَ مِنْ أُمِّهِ، وَكَانَ ذَلِكَ أَوَّلَ مَا نَقَمُوا عَلَيْهِ، لِأَنَّهُ وَلَّى أَقَارِبَهُ الْوِلَايَاتِ. وَقَدْ رُوِيَ حِكَايَةً أَنَّ الْوَلِيدَ صَلَّى بِهِمْ صَلَاةَ الصُّبْحِ أَرْبَعَ رَكَعَاتٍ وَهُوَ سَكْرَانُ، ثُمَّ الْتَفَتَ إِلَيْهِمْ وَقَالَ: «أَأَزِيدُكُمْ؟». وَفِي سَنَةِ 26 هـ، وَسَّعَ عُثْمَانُ الْمَسْجِدَ الْحَرَامَ وَمَدَّهُ، وَاشْتَرَى الدُّورَ الْمُجَاوِرَةَ لَهُ لِتَوْسِعَتِهِ. وَفِي السَّنَةِ نَفْسِهَا فُتِحَتْ سَابُورُ (وَلَعَلَّهَا شَاپُورُ).

In the year 25 AH, cUthman removed Sacd from Kufa and appointed al-Walid ibn cUqbah ibn Abi Mucayt — and he was a Companion, and a brother of cUthman on his mother’s side - and that was the first thing for which he was disliked; because he appointed his relatives to posts of authority. It has been told as a tale that al-Walid led them in prayer for the dawn prayer with four rakcfat when he was drunk, and that then he turned to them and said, ‘Shall I do more (raka?at) for you?’ In the year 26 AH, cUthman enlarged and extended al-Masjid al-Haram, and bought sites (adjoining it) for the enlargement. In the same year Sabur (possibly Shahpur) was opened.

Pada tahun 27 H, Mu'awiyah mengetuai satu ekspedisi ketenteraan ke Cyprus, dengan membawa pasukan tentera melalui laut. 'Ubadah bin as-Samit turut bersama mereka, dan isterinya, Umm Haram binti Milhan al-Ansariyah (dari golongan Ansar). Beliau terjatuh dari haiwan tunggangannya lalu meninggal dunia di sana sebagai syahid. Nabi ﷺ telah meramalkan pasukan ini untuknya, dan baginda telah berdoa agar beliau termasuk dalam kalangan mereka. Beliau dikebumikan di Cyprus. Pada tahun yang sama, Arrajan dan Darabjird telah dibuka. 'Uthman memecat 'Amr bin al-'As dari Mesir dan melantik 'Abdullah bin Sa'd bin Abi Sarh menggantikannya. Beliau mengetuai satu ekspedisi ke Afrika Utara dan membukanya [kepada Islam], sama ada di dataran mahupun di pergunungan. Setiap orang dalam pasukan itu menerima seribu dinar, dan ada yang meriwayatkan tiga ribu dinar. Kemudian, pada tahun yang sama juga, Andalusia dibuka.

In the year 27 AH, Mucawiyah went on a military expedition to Cyprus, taking the armies by sea. cUbadah ibn as-Samit was with them and his wife, Umm Haram bint Milhan al-Ansariyah (of the Ansar). She fell from her riding beast, and died there as a martyr, and the Prophet, may Allah bless him and grant him peace, had foretold this army for her. He had supplicated for her that she should be of them. She was buried in Cyprus. In that same year Arrajan and Darabjird were opened. cUthman removed cAmr ibn al-cAs from Egypt and appointed cAbdullah ibn Sacd ibn Abi Sarh over it, who led an expedition against northern Africa and opened it [to Islam], both on the plains and in the mountains, and every man in the army received one thousand dinars, and it has also been said, three thousand dinars. Then Andalusia was opened in this same year.