The Belgium frontman has been sidelined with an ankle problem since colliding with team-mate Gareth Barry in the 4-0 Merseyside derby defeat at the end of last month.
Martinez has confirmed Lukaku is close to full fitness, but looks set to have to wait until next month to return to the first team as he will be ineligible to face parent club Chelsea a week on Saturday.
"We had positive news on Romelu," he said. "He's back with us and will be ready very soon - we're looking at next weekend."
The Spaniard also seeing Bryan Oviedo reunited with his team-mates on Monday as the Costa Rica defender recovers from surgery following the double fracture of the leg he sustained in the FA Cup clash at Stevenage.
"Bryan Oviedo was around the lads yesterday with a big smile on his face." he said.
Everton currently sit sixth in the Premier League after being leapfrogged by Tottenham following a 1-0 defeat at White Hart Lane on Sunday.
And the former Wigan Athletic manager is confident his team are not out of the running for a top-four finish.
"The team has been working very well as a defensive unit and we are doing great on the ball," he continued. "We are becoming very strong.
"The league never ceases to surprise us. There are still many, many points to play for.
"It will be an interesting rally from now until the end of the season. There are many aspects to affect each team in the final third.
"Nothing is decided yet. Everything is there to be won.
"We all know there is a real unity in our dressing room with a great core that others follow. There are great characters in there."
Martinez also responded to recent rumours linking loanee Gareth Barry with a permanent move to Arsenal at the end of the season.
"The idea with Gareth was to make sure he could return to his best and enjoy playing for Everton," he added. "We'll sit down in the summer."
Everton welcome resurgent Crystal Palace to Goodison Park on Wednesday.
