The former Barcelona wing-back joined Como on-loan in January after cutting short his spell with Celtic over the first-half of the season.
Valle joins Como for €6m and has penned a four-year deal.
“It’s been a great six months. I’ve settled in really well and I’m very happy here,” Valle said after putting pen to paper.
“Obviously, the prospect of continuing here in Como fills me with joy and pride. I can’t wait to start next season and give my all for this club.”
Como coach Cesc Fabregas also said: “Alex is a talented young defender, and he has proven it in the last six months.
“He has integrated perfectly and in a very short time into the team’s mechanisms, showing all his qualities both defensively and offensively. With him Como has secured one of the most interesting talents of his age who will be very important for the team in the future.”