Azerbaijan's Medzhidov was the favourite and top seed in the draw, but had to make do with a bronze medal as the Italian's Olympic pedigree came to the fore and he snuck in front for a 13-12 win in the last round.
His opponent in Sunday afternoon's final will be Great Britain's Anthony Joshua - who defeated Cammarelle 15-13 in last year's World Championships to book his place at London 2012.
Joshua came past Kazakhstan's Ivan Dychko 13-11 in another tight contest that saw the scores level going into a final round, with Joshua powering to victory with some big shots.
Fly Weight world champion Misha Aloian will finish with a bronze after he was beaten by the unseeded Tugstsogt Nyambayar.
The Mongolian won all three rounds as his highly-fancied Russian opponent struggled to keep his defence in order on the way to a 15-11 defeat.
Nyambayar will face the nerveless 18-year-old Robeisy Ramirez Carrazana of Cuba for the gold medal, after he breezed to a 20-10 success over sixth seed Michael Conlan of Ireland.
John Joe Nevin is hoping to win a second Irish gold of the Games - following women's Light Weight Katie Taylor - after he defeated another world champion, Lazaro Alvarez Estrada, 19-14 in the last four of the Bantam Weight division.
Briton Luke Campbell awaits in the final after he eased past Japan's Satoshi Shimizu 20-11.
Another Irishman, Paddy Barnes, was close to scoring a big upset of his own in his Light Fly Weight semi.
He was pitted against Chinese top seed Zou Shiming, the man who beat him 15-0 at the same stage four years ago on his way to Olympic gold. There was no repeat of that heavy defeat this time, with Barnes only beaten on countback after a 15-15 tie.
Zou's rival in the final is Thailand's Kaeo Pongprayoon, who came past David Ayrapetyan.
Ukraine's world silver medallist Denis Berinchyk pulled off a spectacular last round to reach the Light Welter Weight final with a 29-21 victory over Mongolia's Munkh-Erdene Uranchimeg.
Uranchimeg appeared to be coasting to an upset win as he went into the last three points clear, but Berinchyk poured in the shots and forced his opponent to take two standing counts en route to a clear points win.
Berinchyk will face Cuba's Roniel Iglesias Sotolongo in the final after he defeated Italy's Vincenzo Mangiacapre 15-8.
Home favourite Anthony Ogogo's hopes of Middle Weight gold turned to bronze after he hit the canvas twice on his way to a 16-9 semi-final defeat at the hands of powerful Brazilian Esquiva Falcao Florentino.
Japan's second seed Ryota Murata is next up for Florentino after snatching a 13-12 success over Uzbekistan's Abbos Atoev with a four-point swing in the last round.
Florentino's brother, Yamaguchi, was easily defeated by a score of 23-11 when he came up against Egor Mekhontcev in their Light Heavy Weight contest.
The Russian will challenge Kazakhstani third seed Adilbek Niyazymbetov in the gold-medal match after the latter needed a countback to see off Oleksandr Gvozdyk.
The Heavy Weight showpiece will be contested by Ukraine's number one seed Oleksandr Usyk, who overcame Bulgarian opponent Tervel Pulev 21-5, and Italy's Clemente Russo.
Russo edged Azerbaijan's Teymur Mammadov into the bronze medal positions with a big third round, scoring a 15-13 win having started the bout in negative fashion.
Another Ukrainian, Vasyl Lomachenko, remains on course for Light Weight gold after a 14-11 victory over Cuba's fourth seed Yasnier Toledo Lopez.
His opponent will be Han Soonchul, who defeated Evaldas Petrauskas 18-13.
World number one Welter Weight Taras Shelestyuk could not join the Ukrainian surge for gold after he was undone 11-10 by a tenacious showing from Britain's Fred Evans, who was a popular winner.
Serik Sapiyev made it through to the final following a victory over Andrey Zamkovoy, who like all the semi-final losers took bronze.