Archer was part of the team that defeated newly crowned Heineken Cup champions, and arch-rivals, Leinster 19–9 in the 2011 Magners League Grand Final on 28 May 2011. With Munster A, Archer won the 2011–12 British and Irish Cup. He scored his first try for Munster in a 2011–12 Pro12 league fixture against Ulster on 5 May 2012. He signed a two-year contract extension with Munster in January 2013. In October 2015, Archer was ruled out for a number of months after sustaining a neck injury that required surgery.