Hibs had fallen at the last-four hurdle twice in the last six months but there was to be no repeat against Micky Mellon’s side.
Nisbet netted the opener just before the half-hour mark, placing a shot from the edge of the box beyond Deniz Mehmet, before Christian Doidge, although offside, struck a second.
United had their chances but found Matt Macey unbeatable.
Dundee United v Hibs: Live updates
Last updated: Saturday, 08 May, 2021, 16:16
Hibs take on Dundee United at Hampden this afternoon hoping to reach the Scottish Cup final. We all know what happened the last time these two teams met at the national stadium, but can Jack Ross and his side make it third time lucky in G42?
Should have team news in around 45 minutes - remember, Alex Gogic is suspended while Chris Cadden and Sean Mackie miss out through injury.
Team news is in...
No surprises from Jack Ross who makes a straight swap in midfield with Melker Hallberg coming in for the suspended Alex Gogic.
Macey; McGinn, Porteous, Hanlon; Boyle, Hallberg, Irvine, Newell, Doig; Doidge, Nisbet
Subs: Marciano, Gray, McGregor, Stevenson, Wright, Magennis, Murphy, Laidlaw
Jamie Murphy back in the matchday squad for the first time since March 6. Ethan Laidlaw also named among the substitutes.
Not really a great surprise to see Hallberg replace Gogic; the Swede has been the go-to man in central midfield in the past and he can always be counted on to put in a shift in the engine room. Still joint-third in terms of assists for the Hibees this season along with Newell - could he add to that today?
Dundee United team announced
Mehmet; L Smith, Reynolds, Edwards, Robson; Harkes, Butcher, Fuchs; McNulty, Shankland, Clark.
Subs: Doohan, Sporle, Connolly, Pawlett, Chalmers, Appere, Davidson, Watson, K Smith.
Scott Allan, Chris Cadden, and Stevie Bradley have all travelled despite not being included in the matchday squad.
A little over 20 minutes until kick-off. How are the nerves?
Moments away from kick-off! Hibs in their traditional green and white, and Dundee United also in their home kit of tangerine and black.
And we are off!
Under way at a soggy Hampden