Sinéad trained at RADA.

Theatre credits include: HEDDA GABLER (National Theatre), A MIDSUMMER NIGHT’S DREAM (BBC Scottish Symphony Orchestra Prom/Royal Albert Hall); GIVING (Hampstead Theatre); EVENING AT THE TALK HOUSE (National Theatre); THE HUDSUCKER PROXY (Nuffield Theatre/Liverpool Everyman Playhouse); WASP (Hampstead Theatre); PESTS Winner of the Best Studio Performance Award, Manchester Theatre Awards, 2014 (Royal Exchange/Royal Court/UK Tour); BLURRED LINES (National Theatre); TROUT STANLEY (Southwark Playhouse); A TIME TO REAP (Royal Court Theatre); THE CHANGELING (The Young Vic); THE WAY OF THE WORLD (Sheffield Crucible); THE MASTER AND MARGARITA (Barbican/Tour); ECSTASY (Hampstead Theatre/West End); THE GLASS MENAGERIE (Young Vic); LULU (Gate Theatre/Headlong); EIGENGRAU (Bush Theatre); OUR CLASS (National Theatre); HIS GHOSTLY HEART/LITTLE DOLLS (Bush Theatre); WOMEN OF TROY (National Theatre); THE WILD DUCK Winner of the Ian Charleson 2nd Award for Outstanding Newcomer (Donmar Warehouse); YOU CAN NEVER TELL (Bath/Tour/West End); THE BIRTHDAY PARTY (West End); THE MANDATE (Royal National); THE CRUCIBLE (Crucible Theatre); SPOONFACE STEINBERG (GBS).

Television credits include: CHEWING GUM Series 2 (Retort/E4); IN THE DARK (BBC); TOAST OF LONDON Series 3 (Objective Productions/Channel 4); INSIDE NO. 9 Series 2 (BBC); THE SMOKE (Kudos/Sky 1); WAY TO GO (BBC); BLACK MIRROR Series 2: BE RIGHT BACK (Channel 4); MEN ARE WONDERFUL (BBC); HALF BROKEN THINGS (ITV); IDEAL [5 Series] (Baby Cow/BBC2); TRIAL AND RETRIBUTION (La Plante Productions); WHO GETS THE DOG (Company Pictures); LONDON (BBC); THE HOGFATHER (Sky); VIVA LAS BLACKPOOL (BBC); HE KNEW HE WAS RIGHT (Deep Indigo).

Film credits include: KALEIDOSCOPE (Stigma Films); DAPHNE (The Bureau); FANTASTIC BEASTS (Warner Brothers); THE GIFT [Workshop] (Lonesome Pine Productions); BED TRICK (Young Vic Short Films); MR. TURNER (Thin Man Films/Film 4); WRECKERS (Wreckers Ltd); NANNY MCPHEE AND THE BIG BANG (Working Title); THE BOAT THAT ROCKED (Working Title); SPRING OF 1914 (Praxis); HAPPY GO LUCKY (Thin Man); PRIDE AND PREJUDICE (Working Title); VERA DRAKE Winner of the Golden Lion Award, Venice Film Festival, 2004 (Thin Man).

Sinéad jointly won the Michael Powell award for 'Best Performance in a British Feature Film' with Liv at the Edinburgh International Film Festival in 2018.

Sinéad is represented by Christopher Farrar at Hamilton Hodell.