Richardson's first goals of the season could not have come at a better time for manager Steve Bruce as his attacking options were limited.
However, Bruce had to endure a nervous last few minutes with Charlie Adam pulling a goal back from the penalty spot in the 86th minute.
Richardson's goals put Sunderland in the driving seat in the first half but they were also grateful to goalkeeper Craig Gordon, who made three magnificent saves in that period.
Bruce's side made a flying start and Blackpool were pinned back again in the seventh minute when Jordan Henderson swung in a cross from the right.
Steed Malbranque peeled away from his marker but saw his header clear the bar by some distance.
Sunderland made the breakthrough in the 15th minute following a swift counter-attack.
Asamoah Gyan released Richardson with a delightful through ball and he swept a shot into the net for his first goal this season.
Blackpool were stung and Adam floated in a free-kick seven minutes later but Elliot Grandin's header was easily taken by Gordon.
Sunderland almost added a second in the 26th minute when Henderson clipped the ball to Ahmed El Mahamady on the right flank.
He delivered a deep cross and Richardson was handily placed but just failed to get a vital touch.
Blackpool suddenly broke out of their shell and Gordon made two superb saves in the space of two minutes.
He turned away a close-range shot from Luke Varney in the 28th minute after he was set up by the influential Adam, who is apparently on Liverpool's radar.
Then Adam almost equalised, his effort from the edge of the area being turned over the bar by the Scotland international.
The Black Cats extended their lead in the 35th minute with Richardson's second goal of the game.
Richardson showed good movement to get on the end of a pass from Malbranque and his effort beat Richard Kingson at the goalkeeper's near post.
Sunderland, however, were again grateful to Gordon in the 42nd minute when he pushed over a superb 20-yard free-kick from Adam.
Five minutes later Kingson was left with a cut on his head following a brave block from Zenden, who had been put through by Richardson. He was unable to continue and was replaced by Paul Rachubka between the posts.
It was another blow for manager Ian Holloway, with his side trailing by two goals.
Blackpool responded, though, and almost pulled a goal back in the 59th minute when Varney set up Adam in the six-yard box but Gordon was equal to his effort and turned it over the bar.
Holloway decided to go for broke three minutes later and brought on fit-again striker Marlon Harewood for Grandin.
Harewood was quickly into the action and got the better of Titus Bramble in the 66th minute but dragged his shot the wrong side of the post.
Blackpool were anxious to get back in the game and Adam curled a shot wide from an acute angle in the 77th minute after being picked out by Matt Phillips.
They eventually pulled a goal back in the 85th minute with Adam scoring from the penalty spot after David Vaughan was nudged by Bramble. However, it was too little too late.
