Dia dibaiat sebagai khalifah tiga malam setelah pemakaman Umar. Diriwayatkan bahwa orang-orang berkumpul selama hari-hari itu bersama Abdurrahman bin Auf, memberinya nasihat dan berbicara secara rahasia dengannya. Tidak ada seorang pun yang berakal yang duduk sendirian bersamanya yang melihat ada orang yang setara dengan Utsman. Ketika Abdurrahman duduk untuk membaiat, ia memuji Allah dan berkata dalam pidatonya, "Aku melihat orang-orang menolak siapa pun selain Utsman." Ibnu Asakir meriwayatkannya dari al-Miswar bin Makhramah. Dalam riwayat lain, "Sekarang! Ali, aku telah meneliti di kalangan orang-orang dan aku tidak melihat mereka menginginkan seorang pun yang setara dengan Utsman. Oleh karena itu, janganlah engkau membuka jalan bagi dirimu sendiri." Ia memegang tangan Utsman dan berkata, "Kami membaiatmu sesuai dengan Sunnah Allah, Sunnah Rasul-Nya ﷺ, dan Sunnah dua khalifah setelahnya." Abdurrahman membaiatnya, dan kaum Muhajirin serta kaum Anshar pun membaiatnya.

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 bahwa Anas berkata: 'Umar memanggil Abu Talhah al-Anshari satu jam sebelum ia wafat dan berkata, "Engkau termasuk lima puluh orang dari kaum Anshar bersama kelompok ini, para sahabat musyawarah, karena mereka, menurut keyakinanku, akan berkumpul di sebuah rumah. Berdirilah di pintu itu bersama kawan-kawanmu, jangan biarkan seorang pun masuk, dan jangan biarkan hari ketiga berlalu sebelum mereka mengangkat salah seorang dari mereka untuk memimpin."' Dalam Musnad Ahmad disebutkan bahwa Abu Wa'il berkata: Aku bertanya kepada 'Abdurrahman bin 'Auf, "Bagaimana mungkin engkau membaiat 'Utsman dan mengabaikan 'Ali?" Ia menjawab, "Di mana letak kesalahanku? Aku mulai dengan 'Ali dan aku berkata, 'Apakah aku membaiatmu sesuai Kitabullah, Sunnah Rasul-Nya, dan perbuatan Abu Bakar serta 'Umar?' Ia berkata, 'Sejauh kemampuanku.' Kemudian aku menawarkan hal yang sama kepada 'Utsman, dan ia berkata, 'Ya.'" Diriwayatkan bahwa 'Abdurrahman berkata kepada 'Utsman secara pribadi, "Jika aku tidak membaiatmu, siapakah yang akan engkau tunjuk untukku?" Ia menjawab, "'Ali." Ia berkata kepada 'Ali, "Jika aku tidak membaiatmu, siapakah yang akan engkau tunjuk untukku?" Ia menjawab, "'Utsman." Kemudian ia memanggil az-Zubair dan berkata, "Jika aku tidak membaiatmu, siapakah yang akan engkau tunjuk untukku?" Ia menjawab, "'Ali atau 'Utsman." Kemudian ia memanggil Sa'd dan berkata, "Siapakah yang akan engkau tunjuk untukku?"

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?

"karena, adapun saya dan engkau, kami tidak menginginkannya." Ia berkata, "'Utsman." Kemudian 'Abdurrahman meminta nasihat seluruh tokoh terkemuka dan melihat bahwa kebanyakan dari mereka cenderung kepada 'Utsman.

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.

Ibnu Sa'd dan al-Hakim meriwayatkan bahwa Ibnu Mas'ud, semoga Allah meridhainya, berkata ketika 'Utsman dibaiat, "Kami telah menyerahkan urusan kepada orang terbaik di antara yang tersisa, dan kami tidak lalai." Pada tahun kekhalifahannya ini, Rayy dibuka [untuk Islam]. Sebelumnya wilayah itu pernah dibuka lalu hilang kembali. Pada tahun itu banyak orang mengalami mimisan, sehingga tahun itu dikenal sebagai "Tahun Mimisan." 'Utsman sendiri terkena mimisan hingga ia tidak dapat menunaikan haji dan menunjuk seseorang untuk menggantikannya. Pada tahun itu pula banyak benteng Byzantium yang direbut. Di tahun itu 'Utsman mengangkat Sa'd bin Abi Waqqash sebagai gubernur 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.

Pada tahun 25 H, 'Utsman memberhentikan Sa'd dari Kufah dan mengangkat al-Walid bin 'Uqbah bin Abi Mu'ayt sebagai penggantinya. Ia adalah seorang Sahabat, dan saudara 'Utsman dari pihak ibu. Hal inilah yang pertama kali membuat ia dibenci, karena ia mengangkat kerabatnya ke jabatan-jabatan penting. Diceritakan sebagai kisah bahwa al-Walid pernah memimpin mereka shalat Subuh dengan empat rakaat dalam keadaan mabuk, lalu ia menoleh kepada mereka dan berkata, "Apakah aku perlu menambah lagi (rakaat) untuk kalian?" Pada tahun 26 H, 'Utsman memperluas dan memperbesar Masjidil Haram, dan membeli tanah-tanah di sekitarnya untuk perluasan tersebut. Pada tahun yang sama, Sabur (mungkin Syahpur) berhasil ditaklukkan.

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 melakukan ekspedisi militer ke Siprus dengan membawa pasukan melalui laut. 'Ubadah bin ash-Shamit ikut bersama mereka, dan istrinya, Ummu Haram binti Milhan al-Anshariyah (dari kalangan Anshar). Ia terjatuh dari hewan tunggangannya dan wafat di sana sebagai syahidah. Nabi ﷺ telah memberitahukan tentang pasukan ini untuknya, dan beliau ﷺ telah memohonkan agar ia termasuk di antara mereka. Ia dimakamkan di Siprus. Pada tahun yang sama, Arrajan dan Darabjird dibuka. 'Utsman memberhentikan 'Amr bin al-'Ash dari Mesir dan mengangkat 'Abdullah bin Sa'd bin Abi Sarh sebagai gubernurnya. Ia memimpin ekspedisi ke Afrika Utara dan membukanya [untuk Islam], baik di dataran maupun di pegunungan. Setiap orang dalam pasukan menerima seribu dinar, dan ada pula yang mengatakan tiga ribu dinar. Kemudian Andalusia dibuka pada tahun yang sama.

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.