Boyle attended Holy Child Killiney Secondary School, Co. Dublin, Ireland. A graduate of University College Dublin in archaeology and history, where she was involved in the university society Dramsoc, she trained in costume design at the Abbey Theatre and began her career in the early 1980s. She also did a postgraduate diploma in textiles at West Surrey College of Art & Design (now University for the Creative Arts).
Her many credits include Anne Devlin (1984), December Bride (1991), Into the West (1992), Widows' Peak (1994), Angela's Ashes (1999), Nora (2000), When Brendan Met Trudy (2001), The Iron Lady (2011), Miss Julie (2014) and Testament of Youth (2014). Her collaboration with Stephen Frears began with The Snapper in 1993 and continued with films including Mary Reilly (1996), The Queen (2006), Cheri (2009), Tamara Drewe (2010), Philomena (2013), Florence Foster Jenkins (2016) and, most recently, Victoria & Abdul (2017).
As well as her three Oscar nominations, Boyle has been nominated for several other awards throughout her career as a costume designer and amongst those that she has won are an Emmy Award for the television film The Lion in Winter (2003), a Costume Designers Guild Award for The Queen (2006) and four Irish Film and Television Awards for The Queen (2006), Chéri (2009), The Iron Lady (2011) and Philomena (2013). If she wins the Oscar for which she has been nominated at the 90th Academy Awards (2018), she will become the fifth Irishwoman to win a competitive Oscar after art Director Josie MacAvin, make-up Artist Michèle Burke, Producer Corinne Marrinan and Actress Brenda Fricker. She is married to Donald Taylor Black and they have one child.