The Hammers have slipped to 17th in the Premier League standings with just one win in their last seven league outings.
However, Wednesday saw West Ham book a Capital One Cup semi-final with Manchester City after achieving successive victories at White Hart Lane for the first time since 1966, with a 2-1 win over Tottenham.
Jarvis expects the cup success will give the Hammers an injection of confidence as they look for their first win at Old Trafford since 2007.
West Brom, Everton and Newcastle have beaten the defending champions on home soil this term and Jarvis believes West Ham can add further misery to David Moyes and Manchester United.
"It was a fantastic result and just what we needed," the 27-year-old told the Daily Mirror.
"Now I don't see why we can't get something at Manchester United. Teams have gone there this season and got results.
"At home, we'll try and be as solid as we usually are and try and get some points there. They're still a fantastic side. But we can go there full of confidence."
Despite victory in the league cup, West Ham's top flight form - which has seen them lose four of their last six matches - has put manager Sam Allardyce under intense scrutiny.
Tottenham, Fulham and Crystal Palace have all undergone managerial overhauls in the last month but Jarvis claims the West Ham squad are wholly backing Allardyce to remain at Upton Park.
"I don't think us all backing Sam has ever been in doubt," Jarvis added.
"We work extremely hard and show great team spirit. We back the manager it came out at Spurs.
"The problem is we've just been putting our chances away. We've kept eight clean sheets but we need to score."