The Millers took a massive step towards Championship survival as Matt Derbyshire’s early strike proved enough to see off fellow strugglers Brighton.
Victory moved Rotherham seven points clear of the bottom three – though they have played a game more than both Millwall and Fulham who sit below them – and was enough to send rock bottom Blackpool tumbling into League One.
It took just eight minutes for the Millers to go in front courtesy of Derbyshire’s wonderful near post finish.
And they should have added to their tally in the first half with several chances going begging.
It made for a somewhat nervy second half as Brighton emerged strong but largely lacked real threat.
On-form Derbyshire darted in to meet Jordan Bowery’s fierce cross at the near post and strike a sublime volley past a helpless David Stockdale to get the Millers off to a great start.
Both sides worked well to deny the other opportunities following Derbyshire’s opener.
Brighton’s first effort came from former Miller Chris O’Grady who fired harmlessly wide from 20 yards.
The Millers arguably should have doubled their lead when Kirk Broadfoot headed back across goal to Bowery who could only turn his effort over the bar.
And they missed another great chance with Derbyshire dragging wide after meeting Ben Pringle’s fine cross.
After the break, the visitors came back strongly but lacked a real threat in front of goal.
Brighton were almost gifted an equaliser when Bowery turned a cross from substitute Leon Best into his own goal.
Bowery drilled on goal with a powerful strike at the right end moments later but his effort was wide.
Kari Arnason headed just wide at the back post from a corner while Jack Hunt clipped a low effort just past the post.
Derbyshire drew a superb one-handed stop from Stockdale as the Millers continued to threaten.
Mustapha Carayol fired into the side netting from a Kazenga Lua Lua while substitute Craig Mackail-Smith almost scored with his first touch but was denied by Emilano Martinez.
Brighton pushed hard in search of the leveller and it took a fine diving block from Farrend Rawson to keep out Joe Bennett’s strike.
But Danny Ward could have sealed it for the Millers after coming off the bench, only to see his strike flash past the goal in the last minute.
Rotherham United (4-2-3-1): Martinez; Hunt, Broadfoot, Rawson, Lafferty; Arnason, Smallwood; Bowery (Ward 78), Green, Pringle; Derbyshire.
Subs not used: Collin, Frecklington, Milsom, Newton, Hammill, Rowe.
Brighton: Stockdale, Saltor, Dunk, Stephens, O’Grady (Best 46), Ince, Lua Lua (Mackail-Smith 75), Kayal, Bennett, Carayol (Teixeira 81), Halford.
Subs: Walton, Hughes, Calderon, Forster-Caskey.
Referee: K Wright (Cambridgeshire).