Koeman was shown a red card for comments he supposedly made to the fourth official not long after Granada had drawn level at Camp Nou on Friday (AEST).
The Dutchman then watched on from the stands as the home side conceded again in the 79th minute, substitute Jorge Molina heading home to provide a further twist in the title race.
"I don't understand why they have sent me off. They [said I] have disrespected the fourth official," Koeman said after the match, according to Marca.
"I don't understand the red. According to the delegate, it was a lack of respect for the fourth official. I haven't said anything. I haven't insulted him or anything. But hey, if the fourth official wants to be the star of the night ... thank you."
Barcelona had appeared set to take over at the top of the table but now sits two points behind LaLiga leader Atletico Madrid with five games remaining.
One of those matches sees Barca host Atleti on 9 May (AEST), which will be covered by Koeman's suspension unless his appeal is successful. The other fixture will be Monday's (AEST) no crucial trip to Valencia.
In confirming the appeal, the club referenced that its head coach had not previously been sent off since taking charge.