The three-part series is based on real-life, convicted murderer Malcolm Webster and charts a 13-year period beginning when Webster was planning to poison his first wife.
Sheridan has appeared in numerous TV dramas
Reece Shearsmith takes on the lead role, while Sheridan will star as Webster's first wife, who is being regularly drugged by her new husband.
The 32-year-old actress is no stranger to gritty TV dramas and took on the title role in ITV's 2012 series 'Mrs Biggs'.
Reece previously starred in 'Psychoville' and comedy 'League Of Gentlemen'.
'The Widower' starts on March 17 at 9pm on ITV1.