Keith Harding, the MSP for Mid-Scotland and Fife, said he was proud to be a mason, but that it had "no influence whatsoever" on his political life.
Mr Harding was prompted to register his membership of the masons after the standards committee earlier this week cast what he called "aspersions" on the secret organisation.
Fellow MSPs Phil Gallie, Jamie McGrigor and Brian Monteith later declared themselves as masons but have not registered their memberships with the committee.
Mr Harding said that if a fellow mason tried to influence him in his political role - or in his former role as a magistrate - he would ignore him.
He went on: "I am not afraid to declare the fact that I am a mason and if they (the committee) want to know, then I will tell them.
Life membership
"I feel that we should be proud of the fact we are masons. The implication is that it is wrong to be a mason.
"It is not a secret organisation, but the biggest men's club in the world."
Mr Gallie insisted he would not be declaring his membership in the register of members' interests.
He said: "I joined the freemasons when a youngster but I have not been involved since the early 1960s.
"I make no bones about the fact that I am a life member of the freemasons but I have absolutely no intention of registering that.
"As far as I'm concerned it's got absolutely nothing to do with anyone as far as interests go.
"It's a brotherhood. It's a charitable organisation and they work together to help other people but they don't do it in a way that disadvantages society."
Move welcomed
SNP chief whip, Kay Ullrich, said she was "totally unaware" of whether any members of her party belonged to the organisation.
Ms Marwick welcomed Mr Harding's move and called on all members, including those from her own party, to register their membership.
Euan Robson, the Liberal Democrat chief whip, said: "I can't ever recall a discussion on it. It's not something that I think is particularly interesting to us."
A spokeswoman for the Labour Party said as far as the party was aware none of its MSPs were freemasons.