When the Bill approving the move was passed by MSPs in February, the date for the first gay marriage in Scotland was expected to be in September or October. But campaigners say they now believe it could be mid-December by the time the legislative process is completed.
While Scotland was the first part of the UK to consult on the issue, it has since been 'overtaken' by England and Wales, where the first gay marriages took place two weeks ago.
Tim Hopkins, director of the Equality Network, said a lengthy consultation process in Scotland had led to improved legislation.
But he raised concerns it could take until the middle of November for the secondary legislation to pass through the Scottish Parliament, taking into account issues such as further consultation and the parliamentary recess for the independence referendum.
Mr Hopkins said: "The notice period for marriage, which is currently 14 days, has also been extended to 28 days in the Act.
"So if the secondary legislation passes in the middle of November, then anyone who gives notice they wanted to marry immediately after that wouldn't be able to marry until at least the middle of December."
He added: "One of the things we have suggested is maybe the Scottish Government could consult on the secondary legislation for less than the standard practice of three months.
"Essentially we are saying people are getting very frustrated and you should do it as quickly as you can.
"I think right at the moment people are feeling particularly frustrated as they have seen what has been happening down south."
Composer Benjamin Till's marriage to Nathan Taylor was one of the first same-sex ceremonies to take place in England and Wales and was broadcast on Channel 4's Our Gay Wedding: The Musical.
He said he had been contacted by viewers in Scotland after the programme was screened who expressed frustration that gay marriages were not yet happening in Scotland.
Mr Till added: "It seems a little ludicrous that things aren't moving at the same pace, and a little sad for the Scots."
Labour health spokeswoman Jackie Baillie said: "LGBT couples in Scotland have had to wait too long for marriage equality. Any additional delays are simply unacceptable."
A spokesman for the Scottish Conservatives said: "Now that the legislation for same sex marriages has passed, the Scottish Government needs to publish its timetable for the introduction of ceremonies."
Health secretary Alex Neil said: "We have been thorough in making sure we get this legislation absolutely right to ensure everyone had a chance to have their say.
"Now our Bill has received Royal Assent, we are continuing to move forward to implement the statutory changes necessary to ensure that same sex couples have the same rights and privileges as every other married couple."
Neil also pointed out one key change required was the amendment of the Equality Act, a power which is reserved to Westminster. This is to enshrine the right of any religious bodies or celebrants to opt-out of carrying out same-sex marriages in Scotland.