Centre-back Vermaelen is currently plying his trade in the Premier League with Arsenal but his compatriot Mertens is keen to see him make the switch to Serie A.
Following Arsenal's meeting with Napoli in the Champions League group stages, Mertens has led the calls to bring the Ajax academy graduate to Italy.
Mertens revealed he has spoken several times with his international colleague about the switch and claims Napoli coach Rafael Benitez has also asked him to tempt Vermaelen.
"I have already told Vermaelen to come to Napoli 10 times," he told Belgian newspaper Knack.
"The city is magnificent and even Benitez asked me to convince Vermaelen to come here.
"But Arsenal is a great club and it won't be so easy for him to leave."
Mertens joined Napoli from Dutch side PSV Eindhoven in the summer and became Benitez's first signing at the club, with the Spaniard assuming the reins from Walter Mazzarri.
"The club contacted me but also he called me about how keen he was to sign me," he explained.
"That played a role in my decision, a coach who really wanted me, a financial upgrade, a new league and the Champions League."
Mertens has scored just twice in his 22 appearances since moving to Italy but insists Benitez is playing a pivotal role in helping him to acclimatise to new conditions.
"Benitez was clear to me from the beginning," he added. "He told me how he wanted to play and also said he would like to rotate a lot.
"I had time to adapt myself, another league, another way of playing football.
"Benitez said from the start: 'I will bring you slowly, don't worry'.
"And that is what happened. Therefore I am not annoyed that I haven't played much at the start."