Neil Gillies set up the Highlands and Islands Support Group for Grieving Families in 2002. Two years later he helped form the Suicide Awareness Group.
In addition to forging MSP Mary Scanlon's signature, he was also found guilty of embezzling nearly £7,000 while administering the funds of the two charities.
The Suicide Awareness Group contacted the police after an employee saw cheques for £500 and £2,000 made payable to Gillies.
A two-year investigation by the Office of the Scottish Charity Regulator and police revealed that Gillies had used the money to pay his mortgage.
A spokesman for the OSCR said: "This demonstrates that we have a robust legal framework for dealing with complaints."
The OSCR would publish a report on the case, he added.