[9] On 25 April 2019, Sabah Chief Minister Shafie Apdal announced that Sabah DAP's Vivian Wong Shir Yee, the daughter of the late incumbent, as the candidate for the alliance of Pakatan Harapan (PH), Sabah Heritage Party (WARISAN) and United Pasokmomogun Kadazandusun Murut Organisation (UPKO; later renamed United Progressive Kinabalu Organisation and now component party of PH) for the by-election.

[14] On 26 April, former Batu Sapi MP, Linda Tsen Thau Lin was announced as the PBS candidate.

[17] Somehow STAR had later retracted earlier decision to contest in the by-election in order to support their GBS counterpart and ally, PBS instead.

[25] They also had earlier denied they had met their previous BN coalition partner, UMNO, and declared they would not work with them in the by-election.

[30] United Sabah National Organisation (USNO) also declared they would not contest and would support the PBS candidate in the by-election.

[31] Businessman and former oil palm company manager Chia Siew Yung, 46, announced he would be contesting in the by-election as an independent.

[9] Sulaiman Abdul Samat, 36, the ex-Assistant Administrator of DAP Sandakan Parliament Service Centre, had also intended to join the by-election.

[33] On 27 April Nomination Day, Vivian Wong of DAP and Linda Tsen of PBS along with 3 independents, Chia Siew Yung (key), Hamzah Abdullah (tree) and Sulaiman Abdul Samat (chair) filed their nomination papers to set for a five-cornered fight in the by-election.

[34] Finance Minister, Lim Guan Eng announced a RM2.28 billion development project to be held in Sandakan.

[36] PBS put up a controversial banner that claimed Finance Minister Lim Guan Eng had threatened Sandakan voters by saying he could not solve the issue of insufficient parking lots at the Sandakan Hospital in the event that DAP's candidate Vivian Wong lost in this by-election.