Originally Plying Between Eunos Terminal at Old Jalan Eunos and Labrador Park Terminal.
Service 51 and 54 integrated on 22nd March 1987 when Eunos Terminal was moved from Old Jalan Eunos to the location of the present-day Eunos Bus Interchange and Service 51 was extended to Hougang (South) Int.
On 18th December 1988, with the extension of the MRT to Jurong East, this service was integrated with Service 192 (Jurong - South Canal) to form Service 51 and extended to Jurong East.
Between Hougang South Interchange and Jurong East interchange.
On Sunday 12 May 2002, amended to ply Pandan Gardens.
On Sunday 15 February 2004, with the closure of Hougang South Int, this service was extended to Hougang Central Interchange via Hougang Ave 3 and Upp Serangoon Rd.