The 22-year-old Senegal midfielder had already completed his medical with Chelsea, but the deal collapsed shortly after the 23:00 BST transfer deadline.
Chelsea targeted Camara to bolster their midfield options as Enzo Fernandez was closing in on a record £125m switch to Manchester City.
Despite missing out on Camara, the club completed several major signings this window, including record signing Morgan Rogers from Aston Villa and goalkeeper Emiliano Martinez.
Alonso's side has won all three of their matches so far this season in the Premier League and advanced in the Carabao Cup.
