The Swede, who ditched the heptathlon in favour of the long jump in 2008, has struggled in her new event since tearing a hamstring last July and was well behind defending champion Lyudmila Kolchanova who topped qualifying with 6.87.
Kluft was given a wildcard into the Swedish team after failing to meet the entry standard and the 27-year-old was clearly ecstatic after her opening jump, pumping her fist as she walked out of the pit.
"It's a big victory," a beaming Kluft told reporters after she became the final qualifier for Wednesday's final.
"After being injured for such a long time to be in a big championship again, that feels so great. This is what sport is about, so for me, even if I'm 12th into the final I'm still very very happy."
Russian teenager Stanislav Yemelyanov also had reason to be cheerful, taking the first gold medal of this week's championships with victory in the men's 20KM walk in his first season competing as a senior.
Yemelyanov finished in a time of one hour, 20 minutes and 10 seconds with Italy's 50KM walk Olympic champion Alex Schwazer 28 seconds behind. Portugal's Joao Vieira finished third to repeat his bronze medal of four years ago.
"I tried to catch up with Yemelyanov but he was in top shape today. Now I hope to recover in time for the 50KM walk," said Schwazer, who is also entered in Friday's longer event.
The 19-year-old Yemelyanov, who was never out of the top two, raised his arms aloft as he crossed the line after 20 laps on Barcelona's streets and was immediately handed a Russian flag, which he draped around his shoulders.
The women's shot put and the men's 10,000 metres are the other finals on Tuesday. Germany's triple world silver medallist Nadine Kleinert topped the morning's qualifying with 18.98 metres but Belarus's Nadezhda Ostapchuk, who leads the 2010 European standings with a throw of 20.95 has won all eight of her competitions this season.
Medal favourite Jonathan Borlee safely reached the semifinals of the men's 400 metres as did fellow contenders Martyn Rooney of Britain and Ireland's David Gillick. Borlee, the fastest European this year, won his heat in 45.91 but was 0.2 seconds slower than his identical twin Kevin who took the first race in 45.71.
Top-ranked European Natalya Antyukh of Russia won her 400 hurdles heat by over a second in 54.29 to record the fastest time in qualifying. Slovakian Libor Charfreitag was the best qualifier in the men's hammer with 77.70 and Nicoleta Grasu of Romania headed the women's discus qualifying competition with 62.10.