Manchester United went ahead against Chelsea in the sixth minute, with Casemiro rising to head home a pinpoint delivery from Christian Eriksen.
Martial then doubled his side’s advantage just before half-time, with the 27-year-old scoring after a devastating injury to Antony.
And late goals from Fernandes and Rashford added gloss to the Red Devils’ display, with Felix scoring a fine consolation for the Blues.
It was a good night for United, who have now qualified for next season’s Champions League.
However, injuries to Antony and Luke Shaw cast a cloud over proceedings - with the pair both doubts for next month’s FA Cup final showdown with Manchester City.
And Ten Hag, when quizzed on the duo by Sky Sports, kept it vague by saying: “It is difficult to say. Let’s wait for 24 hours and then we will know more.”
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On his side getting the win, he said: “It’s important, this club belongs in the Champions League. It’s a massive performance when you get this done.
“First goal was a set play, then we were dangerous on counters.
“Second goal could have been earlier. It was late in the first half.”
United are next in action against Fulham on Sunday as they look to finish their season on a high.
But Ten Hag is adamant his side will be taking the match seriously, despite having Champions League football all wrapped up.
“Sunday is important, we still can be third in the league and we can keep our rhythm,” he said.
Bruno Fernandes also reacted to the win - but insisted there was more to come from his side in the future.
“Getting the Champions League] is decent, it's not perfect because we want more,” said the Portugal international.
“For what we did this season it's perfect. We get the trophy which was our goal after seeing we couldn't get the Premier League.
“Now it's about finishing the league well and going to FA Cup."
When quizzed directly about pipping Liverpool to a place in the top four, he added: "We know it means a lot [to the fans].
“For us it's about getting our goals. We know we'd be happy also for Liverpool to not be there but for us it's about getting the best for ourselves."
On playing Man City in the FA Cup final, he said: "It's about winning the trophy.
“We have to take the trophy away from someone. We want to win the FA Cup.
“We know it's really important here.
“We know if we win it we stop the option for City getting the treble but for us it's about getting another trophy."
