Tickets for the big fight at Titanic Belfast on 6 September went on sale at 10am on Saturday, but some ticket categories sold out almost immediately.
A purpose-built arena, with a capacity of 16,000, is set to be constructed on the slipway - with Frampton aiming to win the IBF super-bantamweight world title in front of fans in his home city.
"It's unbelievable the response we've had - I knew I had fantastic fans, but this is another level!" Frampton said.
"It proves once again that Belfast has the best boxing fans in the world. September the 6th is going to be a massive night!"
To have sold this many tickets in the first day shows just how popular Carl Frampton has become - he's a superstar in the making.
Cyclone Promotions CEO Barry McGuigan was also delighted with the first-day sales.
"We knew that Carl was a big ticket seller, but this response is unparalleled," he said.
Martínez, who was knocked out in the ninth round last time he met Frampton in the ring, insists their previous encounter simply caught him on "a bad day".
But Frampton has not been shaken by the Spaniard's confidence and, although he admits the fight will be tough, he is sure the outcome will not be any different second time around.
Some tickets in other brackets are still available for the Titanic Showdown.