The Owls enjoyed an outstanding run in April, taking 19 points from a possible 21 in a fine seven-match unbeaten streak featuring six wins and sealing a playoff place.
Carvalhal, whose award marks his first monthly recognition since joining Wednesday, told the EFL: "Sheffield Wednesday fans know that I prefer the collective awards more than the individual, because football is a collective sport.
"I need to thank the players, the fans, the cook, because I'm part of a big group that tries every day to be better and better. This is what the prize represents to me, a collective award that we're very proud to receive."
Kermorgant, meanwhile, enjoyed a particularly productive April with seven goals in as many games, which helped the Royals to third in the table with one game to go.
The 35-year-old, who has announced that he will retire from football at the end of next season, said: "It feels great to win the Player of the Month award, I'm really proud of it as it's my first individual trophy.
"We've done really well in April so I'm pleased to be performing for the last month of the season."
Carvalhal beat Nigel Clough, Lee Johnson and Slavisa Jokanovic to the manager's accolade, while Kermorgant saw off competition from John Brayford, Stefan Johansen and Glenn Murray for the player gong.