On November 28th 2017, the Canadian Senate began the debate about Bill C-45, which would eventually become the Cannabis Act.

The first and second reading of the bill went through an astronomical 15 sessions between November 28 and March 22nd. The third reading of the Bill occurred between March 31st and June 7th over the course of 6 sessions. To put this into perspective, the Impact Assessment Act, which governs environmental and other assessments of major infrastructure projects went through only 3 sessions upon third reading in the Senate.

On May 31, 2018, debate began at third reading. Pursuant to a motion adopted in the Chamber, speeches and amendments were grouped thematically:

• May 31: issues relating to cannabis production
• June 1: issues relating to the sale and distribution of cannabis
• June 4: international issues relating to cannabis
• June 5: issues relating to criminal penalties
• June 6: issues relating to cannabis consumption, public health and matters relating to Indigenous peoples.

The vote at third reading took place on June 7, 2018. Bill C-45, as amended, was adopted by a vote of 56 to 30, with one abstention. The House of Commons accepted some of the Senate's amendments.

On June 19, 2018, senators voted 52 to 29, with two abstentions, to adopt a motion to inform the House of Commons that the Senate would not insist on amendments with which the House had disagreed.

This historic vote paved the way for the Trudeau led government to put into motion The Cannabis Act.