The new rule will come into force on March 6 on a trial basis until the end of the 2020/21 campaign.
The decision comes following an announcement by the International Football Association Board (IFAB) in December 2020 signalling the go-ahead for competition organisers to trial the system between January and August 2021.
The news was confirmed a day after former Scotland and Manchester United defender Gordon McQueen was diagnosed with vascular dementia.
SPFL chief executive Neil Doncaster welcomed the approval of the new rule, adding: "The safety and wellbeing of players is clearly of the utmost importance to everyone involved with running football.
"Yesterday's tragic news that Gordon McQueen has been diagnosed with dementia is the latest reminder of why it is vital that we do everything we can to protect those playing our game.
"We have seen a great deal of positive development in concussion protocols across sport in recent years and we hope that our participation in this trial will be the next step in that process.”
Each team will be allowed a maximum of two concussion substitutes per match, in addition to the number of permitted substitutes.
When a player sustains a head injury, or suspected concussion, teams may use one of their existing substitutes if the maximum permitted number has not already been used, or make an additional replacement.
If a concussion substitute is made, the opposing team has the option to also make an additional substitution for any reason.