The museum was officially inaugurated on 18 December 1976, within the former Alfa Romeo Arese factory area, where car production ended in 2002 and engine production in 2006. It underwent closures for renovation in 2009 and 2011, with restoration work beginning in the summer of 2014. The renovated structure, reopened on 24 June 2015, features Alfa red projecting roofs added to the original 1970s building and hosted the press unveiling of the all-new Alfa Romeo Giulia and Alfa Romeo logo. The museum reopened to the public on 30 June 2015.
The museum spans 4,800 square metres (52,000 sq ft) and is divided into four theme areas. These areas cover the history of Alfa Romeo road cars since 1910, prototypes and dream cars, aircraft and aeronautical projects, and scale models and awards. The collection includes over 250 cars and 150 engines, with approximately half on display, ensuring at least one example of each model produced is present alongside prototypes and racing cars. Cars from the museum are regularly loaned for events such as the Pebble Beach Concours d'Elegance, the Goodwood Festival of Speed and the Mille Miglia. The 2015 exhibit includes 69 cars.
Scuderia del Portello, an Italian sports association dedicated to Alfa Romeo cars in motorsport and rallies, is located at the Museo Alfa Romeo in Arese. Founded on February 3, 1982, by Luca Grandori, Edilberto Mandelli, Pietro Rondo, Giorgio Schoen, Stefano Senin and Renato Ughi, the Scuderia initially supported drivers racing older Alfa Romeo models. The name recalled the suburbs of Milan where the company’s first factories were built. In 1990, the Scuderia broadened its activities to include modern racing cars and became an official club of the brand management, changing its logo to reflect the form of the Alfa Romeo 1900 radiator. The current president and team principal is Marco Cajani.
The Scuderia del Portello has won multiple FIA Historic Racing Championships, including the European Cup for Historic GT Cars and the European Challenge for Historic Touring Cars. Beyond FIA championships, they have secured eight Italian Historic Car Championships and over 300 overall class victories in European and National historical car races. In 1997, the Scuderia won the Tour Auto with Cajani-Faraci (Alfa Romeo Giulietta Sprint Veloce), and in 2004, 2006, and 2007 the Tour de España, with Jean Sage (Alfa Romeo Giulietta Ti), Sage-Entremont (Alfa Romeo 1900 Ti) and Cajani-Confaloni (Alfa Romeo 1900 CSS Zagato) respectively.
The Scuderia has also participated in commemorations of races like the Carrera Panamericana (winning in the Sport Menor category in 1991 with Arturo Merzario and Vinicio Marta in an Alfa Romeo Giulietta Spider Veloce) and the London–Sydney Marathon. In 2004, the Scuderia achieved class victory at Le Mans Classic with Phil Hill driving an Alfa Romeo 6C 3000 CMM. Relevant drivers associated with the Scuderia del Portello include Bruno Bonini, Costantino Bertuzzi, Angelo Renato Chiapparini, Vic Elford, Carlo Facetti, Fabio Francia, Giovanni "Nanni" Galli, Arturo Merzario, Sandro Munari, Gino Munaron, Fabian Peroni, Gian Luigi Picchi, Luigi "Gino" Pozzo, Gian Claudio "Clay" Regazzoni, Alessandro Sgarzi, Prisca Taruffi, Nino Vaccarella and Ross Zampatti.