League One and Two clubs will be able to field five substitutes during games this season after clubs voted on the ruling.
Championship clubs voted against the proposal, so will stick with three substitutes.
But League One clubs Airdrie and Clyde, and Albion Rovers in League Two will have more of a chance to switch their players when the season kicks off on October 17.
It was also voted that teams in play-off games will only have the use of three substitutes, though one extra per team is permitted should the tie go to extra time.
Premiership clubs currently have the option of using five substitutes, and that is the case in the Betfred and Challenge Cups, with the option of one further change in extra time.
The SPFL needed eight out of 10 clubs in League One to vote for five subs, and nine responded positively. All 10 League Two clubs voted for the additional changes.
For the play-offs, SPFL needed positive responses from nine out of 12 Premiership clubs, eight out of 10 Championship clubs and 15 of 20 in Leagues One and Two, but they only got eight Premiership clubs, four in the Championship and although 19 of the 20 League One and Two clubs voted for it, they were over-ruled.
A SPFL spokesman said: "In line with last season, FIFA has allowed each league to determine its own rules regarding the use of substitutes for Season 2020/21, due to Covid-19.
"As a members’ organisation, it is important that the clubs in each division decide issues such as this for themselves."
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