Garrido was appointed at the beginning of December to replace Pepe Mel, who has since taken over at Premier League side West Bromwich Albion, but has failed to lift the Seville-based club off the bottom.
"President Miguel Guillen has just informed (Garrido) that the club has decided to dispense with his services," Betis said in a statement on their website (www.realbetisbalompie.es).
"The coach, who has not obtained the desired results, will not be in charge of the team tomorrow," they added.
"The board's intention is that the new coach, who will arrive tonight, will sign his contract and immediately take the reins of the team."
Betis qualified for the Europa League after finishing seventh in La Liga last season and will play Russian side Rubin Kazan over two legs in the last 32 next month.
However, they are five points adrift at the bottom of Spain's top division with just over half the season played and were thrashed 5-0 at home to Real Madrid on Saturday.
It was their fourth defeat in five La Liga games under Garrido, a former Villarreal and Club Bruges coach, and the Betis fans chanted for him to be fired and sang Mel's name at their Benito Villamarin stadium.
Betis have lined up Argentine Gabriel Humberto Calderon to take over from Garrido, Spanish media reported.