Tanggal 17 Agustus 2015, Diamanti dipinjamkan oleh Guangzhou Evergrande ke tim Liga Utama Inggris [[Watford F.C.|Watford]] karena aturan yang membatasi jumlah pemain internasional di klub itu.<ref>{{cite news|url=http://www.watfordfc.com/news/article/150806-alessandro-diamanti-signs-for-watford-fc-2599122.aspx|title=OFFICIAL: Diamanti Transfer Completed|date=17-08-2015|accessdate=17-08-2015|publisher=Watford FC|language=bahasa Inggris|archive-date=2015-08-17|archive-url=https://web.archive.org/web/20150817234511/http://www.watfordfc.com/news/article/150806-alessandro-diamanti-signs-for-watford-fc-2599122.aspx|dead-url=yes}}</ref><ref>{{cite news|url=http://www.bbc.co.uk/sport/0/football/33905684|title=Alessandro Diamanti: Watford sign ex-Italy and West Ham midfielder|date=17-08-2015|accessdate=17-08-2015 |publisher=BBC Sport |language=bahasa Inggris}}</ref>
