The by-election was held on 14 May and 23 July for Radin Mas and Bukit Merah constituencies respectively. The by-election were called following the deaths of its respective MPs Govindasamy Naidu and Lim Guan Hoo.

1977 Singaporean by-elections

← 1970 14 May 1977 (Radin Mas) 23 July 1977 (Bukit Merah) 1979 →
2 seats to the Parliament of Singapore
Registered	35,412
Turnout	33,897 (95.72%) 1.27%
First party Second party Third party   Leader Lee Kuan Yew J. B. Jeyaretnam Lee Siew Choh Party PAP WP BS Seats won 2 0 0 Seat change Popular vote 23,678 5,021 4,473 Percentage 71.38% 15.14% 13.48% Swing 4.62% 2.69% 13.48%
MPs before election N. Govindasamy Naidu Lim Guan Hoo PAP Elected MPs Bernard Chin Tien Lap Lim Chee Onn PAP

On 13 February, Bukit Merah MP Lim Guan Hoo suffered compilations from stroke, and on the following day, N. Govindasamy Naidu died in office.

While there were plans for a multi-cornered contest, Workers' Party secretary-general J. B. Jeyaretnam stepped forward to contest the ward against its PAP candidate Bernard Chen Tien Lap, a former civil servant. An independent candidate attempted to contest but was disqualified for the absence in electoral register.

On 30 June, more than a month after the first by-election, Lim Guan Hoo died. Like its first by-election, negotiations for opposition party to contest the ward took place and to avoid a multi-cornered contest, this time being Lee Siew Choh of the Barisan Sosialis party. The PAP fielded civilist Lim Chee Oon to defend the seat.

• Background of First 1977 By election^[usurped]
• Background of Second 1977 By election^[usurped]
• Results of First 1977 By election
• Results of Second 1977 By election