Napoli president Aurelio De Laurentiis took to social media sites to reveal the news Napoli fans, some of whom greeted Higuain at a Rome airport, had been waiting for all day.
“Higuain and Reina have passed their medicals and will soon join the group,” said De Laurentiis on Twitter.
“We can say that we’ve worked really hard but we’re not stopping there!”
Real Madrid forward Higuain, a reported target for both Arsenal and Juventus, is reported to be costing Napoli 37 million euros ($49 million) plus an extra 3 million euros based on bonuses.
Reina joins on loan from Liverpool and will link up with his former Anfield boss Rafael Benitez, who joined the Italians in the close season.
“He’s delighted to rediscover the coach Benitez who he knows from five years in Spain and England and with whom he worked very well,” said Reina’s manager Manuel Quilon.
Last week Napoli sold Uruguay forward Edinson Cavani to Paris Saint-Germain for a French record 64 million euros.