Although Boro saw plenty of the ball they didn't threaten United and looked low on confidence.
In response, the visitors dropped incredibly deep and were even playing with six defenders at one stage, but despite some nervy moments the Red Devils hung on and even added a third through Antonio Valencia in stoppage time thanks to a comical error from former United goalkeeper Victor Valdes.
United fans can finally see something positive paid off after a long streak of being sixth in the EPL.
Towering midfielder Marouane Fellaini broke the deadlock in the 30th minute of the game when he headed a goal from a tight angle.
Manchester United have defeated Middlesbrough 3-1 at the Riverside Stadium for their landmark 600th Premier League victory.
They at least ended their lengthy goal drought as Gestede pounced on a mistake by Chris Smalling to halve the arrears.
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The U.S. trade deficit with Germany was $64.9 billion previous year , the lowest since 2009, according to the Commerce Department. Mr Spicer was very apologetic when confronted by Mr Darroch at a White House dinner on Thursday, the Western diplomat said.
United might be in fifth place, but they also have two fewer games than Liverpool (Fourth place) and one less game than Chelsea, Tottenham and Manchester City (top three).
When asked if a top four finish is key, Mourinho responded: "Yes, it is important for us". Who knows we are going to win the Europa League?
Boro began the second half in much the same fashion as they did the first, enjoying close to 57 per cent of the possession, but without finding a way to cause any trouble for De Gea, with United's defence staying resolute.
Admittedly not speaking his native tongue, Mourinho stumbled over his words - or letters, rather - when attempting to use a metaphor to praise his team's attitude after Sunday's 3-1 win over Middlesbrough. I prefer Europa League. "Manchester United boss Jose Mourinho: "(It's a) big win because it keeps us alive in the fourth position race.
As well as the possibility of finishing in the top four, they have a second chance of competing in next season's Champions League by winning the Europa League, for which they are the bookmakers' favourites.
Next week, there will not be any Premier League action due to the worldwide break.