They will be joined in the top flight next season by Serie B champions Parma, who made sure of their promotion at the start of the month.
Como suffered multiple bankruptcies and tumbled down the pyramid after being relegated from Serie A little over two decades ago.
The club from Lombardy have former Arsenal teammates Cesc Fabregas and Thierry Henry as minority shareholders, with ex-Chelsea midfielder Dennis Wise a board member.
Como only returned to professional football with their promotion to Serie C in 2019. But, bankrolled by Indonesian tobacco giants Djarum, they have stormed through the divisions.
The third promoted club will be decided by playoffs featuring the teams finishing between third and eighth, which include Venezia and Sampdoria.