The Marlins went 21-8 in May, setting a club record for wins in any month.
The road ahead could be more challenging, with a three-game set starting on Friday at Philadelphia, followed by a homestand with the Braves, Rays and Red Sox.
"The last two weeks and last month, we're playing good teams," manager Ozzie Guillen said. "Teams over .500. San Francisco, they have one of the best pitching staffs. We've played Cleveland. We've played Atlanta, Washington. I don't think we've had an easy team yet."
Staying level, the manager notes, will be pivotal.
"Don't get too high, don't get too low," Guillen said. "Show up every day with the same attitude, same enthusiasm. Make every pitch and every at-bat count -- that's how you survive in this game, no matter who is on the mound. No matter how we play. Good teams are going to compete against good teams. Every month that goes by, the harder it's going to get."