Chelsea extended their unbeaten run to 16 games in Europa League after Pedro's equalizer was enough to cancel out Luka Jovic's opener and to snatch a vital away goal.
The "Eagles" needed some time to assume control on home soil as Filip Kostic and Luka Jovic missed two chances in the opening period.
However, the hosts' lively opening period were rewarded with 23 minutes played when Filip Kostic's pinpoint cross into the box allowed Luka Jovic to head the ball past Chelsea goalkeeper Kepa.
Chelsea responded well and increased the pressure as Pedro pulled wide from promising position moments later before Ruben Loftus-Cheek missed the target from inside the box in the 42nd minute.
The visitor's efforts paid off just before the break, as Frankfurt failed to clear the ball from the area allowing Pedro to slot home the leveller from the edge of the box.
After the restart, Chelsea took over and pressed Frankfurt into the defence as Luftus-Cheek came close while David Luiz rattled the woodwork following a free kick at the hour mark.
Frankfurt were unable to put up resistance whereas Chelsea gained the upperhand. However, neither David Luiz nor Luftus-Cheek were able to make the most of their chances.
The hosts came back to life in the closing period as substitute Goncalo Paciencia squandered Danny da Costa's build up work before David Abraham missed the goal from five meters by header in the closing period.
With the 1-1 draw, Chelsea hold the advantage of an away goal meanwhile Frankfurt will either need a higher draw than a 1-1 or a victory to progress into the final.
"We were in a bit of trouble in the opening period but as the match progressed we dominated. We scored just before the break, which was important. We had then the ambition to win the game in the second half," Chelsea's captain Cesar Azpilicueta said.
