"Everybody is fit, everybody is ready," Guardiola told reporters on Friday.
"Manuel (Akanji) is back as well. The busy period is here, and the Champions League is around the corner. It's good to have everyone."
Haaland, the league's joint top scorer with 14 goals with Liverpool's Mohamed Salah, came off the bench in City's 3-1 victory over Burnley on Wednesday, his first action since breaking a bone in his foot against Aston Villa on December 6th.
Guardiola was asked about Spanish media reports claiming Haaland is unhappy at City.
"We don't have the feeling he is unhappy. Maybe the media in Spain has more information than us," the manager said.
After a sluggish start to the season, holders City have won five of their last six Premier League matches, and are second in the table with 46 points, five behind leaders Liverpool but with a game in hand. Guardiola's side are also in the thick of the Champions League and FA Cup.
Brentford are 15th with 22 points, four points above the drop zone, but the Bees have been bolstered by the return of England striker Ivan Toney from an eight-month ban for betting offences.
Wearing the captain's armband, the 27-year-old scored 19 minutes into his comeback on January 20th against Nottingham Forest.
"He is an exceptional player. He is an extraordinary player," Guardiola said of Toney.
"I'm happy he is back and hopefully that period is forgotten. Exceptional players are more than welcome in the Premier League."
Guardiola is expecting Brentford to be tough to beat.
"We know in the past how difficult they have been," he said.
"Even when we won it was tight, we lost twice last season. We know the standards they have, they have a plan and they apply it well. It's another game to face and another challenge."
City return to Champions League action when travel to Copenhagen for the first leg of their last 16 tie on February 13th. They also travel to Luton Town for a fifth-round FA Cup game on February 28th.
