Mr Macron appeared to make his own unidentified hand sign back as the pair met during a working dinner for European leaders on the reform of Europe in Tallinn, Estonia.
Today, Mrs Merkel was seen to make the gesture again at a table opposite British Prime Minister Theresa May, as the talks continued.
The “diamond” hand gesture, Mrs Merkel, is often seen making, is described by conspiracy theorists as a secret code to other members of the alleged Illuminati.
It is alleged by believers of the Illuminati that it is a secret organisation made up of world government and business leaders and celebrities, which actually run all world governments from behind the scenes, and plan to introduce a New World Order which will see just one government running the entire world.
The conspiracy varies, but at its most extreme, the Illuminati is allegedly a Satanic group which uses hand signals to identify members to each other.
One version supported by ex-BBC Grandstand presenter turned conspiracy theorist, David Icke, even claims members of the world’s elite are actually reptilian aliens disguised as humans.
The German Chancellor is known for making her infamous “diamond” hand sign, which has been branded of masonic-style and a symbol of the alleged Illuminati by conspiracy theorists.
However, Mr Macron and Mrs May did not appear to return the gesture.
Mrs Merkel’s use of the sign often attracts attention and she was last seen doing it at the G20 talks in front of Donald Trump and then again in front of Prince William and the Duchess of Cambridge, both in July.
The G20 Summit is identified on several conspiracy theory websites as a key Illuminati meeting, alongside the World Economic Forum and the secretive Bilderberg Meeting.
Others photographed previously using the hand sign in the rhombus shape have included Mrs May and European Commission President Jean Claude Juncker.
The sign is often referred to as a Merkel Diamond, due to her frequent use of it.
Mrs May was snapped imitating the hand gesture while giving a speech outside the Palace of Westminster on July 11 last year.
Conspiracy theory website illuminatiRex lists the diamond sign as number one out of a top-ten of illuminati signs, with Mrs Merkel given her own section for doing it in reverse, in what it describes as the Angela Merkel Raute.
And on the conspiracy theory forum run by David Icke, the significance of the Merkel Diamond, which has been used in political poster campaigns, has been discussed.
A senior forum member with the user name Posidon posted: “I don’t know if anyone ever noticed the Angela Merkel famous hand sign?
“I found today a new picture of it in my local newspaper, and I found curious that they use her hand sign in a political campaign.
“Diamond they say? So I ask, is every one asleep these days?
“Just the first time I saw the image, I noticed it is not a diamond at all, plus the way she placed her fingers (which is not even easy) unless you really want them to be that way does not resemble a diamond at all, but a Masonic symbol of the compass and square.
“Is every one asleep? No one sees and talks about these things, is it not evident enough?”
But Mrs Merkel, who has led the Christian Democratic Union party for 16 years, explained the reason she makes the unusual gesture in a 2013 interview, and denied there was anything sinister behind it.
She told a German magazine: “There was always the question, what to do with your arms, and that’s how it came about. It contains a certain symmetry.”
Other famous faces including Gordon Brown, the Duchess of Cornwall and Recep Tayyip Erdogan have also been spotted making the ‘Merkel diamond’.
US President Donald Trump has previously made other hand gestures which have been alleged to be Illuminati signs.
Some conspiracy theorists claim Mr Trump is a fully signed up member of the Illuminati, but others believe he is an enemy of the Illuminati who has managed to infiltrate its top position – the US presidency.