Halmstads BK and AFC Eskilstuna were relegated at the end of the 2017 season after finishing in the bottom two places of the table. They were replaced by 2017 Superettan champions IF Brommapojkarna and runners-up Dalkurd FF. IF Brommapojkarna returned to Allsvenskan after three years' absence, having been relegated at the end of the 2014 season. This is IF Brommapojkarna's sixth season in the league. Dalkurd FF are participating in the league for the first time in the club's history; they are the fourth new club in the last five Allsvenskan seasons (following Falkenbergs FF in 2014, Östersunds FK in 2016 and AFC Eskilstuna in 2017).