Patrice Garande's side sealed a return to the top flight by claiming third spot in Ligue 2 last season.
Duhamel was a key figure, finishing as the second tier's joint top-scorer with 24 goals in 35 games, while defender Raineau made 17 first-team appearances.
The pair have both signed new two-year deals at the Stade Michel d'Ornano.
"Forward Mathieu Duhamel and full-back Alexander Raineau extended their contract with Caen for two years," the club confirmed on their official website. "They are now linked with the club until June 2016."
Duhamel arrived at Caen in 2012 and has gone on to score 37 goals in Ligue 2, while 27-year-old Raineau came through the club's youth ranks.
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