Pada awal [[musim 2012-13 AC Milan|musim 2012-13]] Gabriel menandatangani kontrak dengan [[AC Milan|Milan]] sebagai cadangan untuk [[Christian Abbiati]] dan [[Marco Amelia]]<ref>{{cite news|title=Adriano Galliani and the Gabriel surprise|url=http://www.acmilan.com/en/news/breaking_news_show/26514|work=acmilan.com|publisher=[[A.C. Milan|Associazione Calcio Milan]]|date=24 May 2012|accessdate=31 July 2012}}</ref><ref>{{cite news|title=Official: AC Milan signs Gabriel from Cruzeiro|url=http://www.goal.com/en/news/69/transfer-zone/2012/05/25/3126229/official-ac-milan-signs-gabriel-from-cruzeiro|work=goal.com|publisher=PERFORM|date=25 May 2012|archiveurl=httphttps://www.webcitation.org/69xTcgCpg?url=http://www.goal.com/en/news/69/transfer-zone/2012/05/25/3126229/official-ac-milan-signs-gabriel-from-cruzeiro|archivedate=16 August 2012-08-16|deadurl=no|accessdate=16 August 2012}}</ref>. Setelah tidak membuat penampilan selama setahun di klub, debut resmi Gabriel datang pada tanggal 19 Oktober 2013 saat [[Massimiliano Allegri]] memilih dia untuk menempati tempat yang ditinggal Abbiati karena cedera, untuk pertandingan kandang melawan [[Udinese Calcio|Udinese]]<ref>{{cite news|title=Stop Abbiati, gioca Gabriel. Amelia titolare con il Barcellona|url=http://www.milannews.it/altre-notizie/stop-abbiati-gioca-gabriel-amelia-titolare-con-il-barcellona-126021|author=Pietro Mazzara|work=milannews.it|date=19 October 2013|accessdate=19 October 2013|language=Italian|archive-date=2013-10-20|archive-url=https://web.archive.org/web/20131020141527/http://www.milannews.it/altre-notizie/stop-abbiati-gioca-gabriel-amelia-titolare-con-il-barcellona-126021|dead-url=yes}}</ref> dan ia bertahan tanpa kebobolan dalam kemenangan 1-0.<ref>{{cite web |title=Milan 1–0 Udinese |url=http://www.legaseriea.it/en/serie-a-tim/match-report/-/match-report/Milan-Udinese/66316 |work=legaseriea.it |publisher=[[Lega Serie A|Lega Nazionale Professionisti Serie A]] |date=19 October 2013 |accessdate=19 October 2013}}</ref>.
