Clubs in the Championship and League One will be able to use five substitutes in matches, starting from this weekend.
It comes after clubs in both divisions voted to extend the rule which is already in place for clubs in the Premiership and League Two.
As part of the resolution, managers will also be able to name a bench of up to nine potential replacements.
The move has been initiated by the SPFL in an effort to minimise the impact of potential fixture congestion due to Covid or weather-related postponements.
League Two sides have been able to use five subs all season but top-flight clubs voted to bring in the rule earlier this month, after their winter break.
An SPFL spokesman said: “Discussions have been ongoing in recent weeks with cinch Championship and cinch League 1 clubs about the potential rule change.
“As a members’ organisation, it is important that clubs in each division are able to make decisions on issues like this for themselves.”
Peterhead manager Jim McInally had been critical of the original decision not to integrate the rule change into all leagues, stating that clubs were playing by different rules.