City midfielder Foden cancelled out Ike Ugbo’s opener in front of first-team coach Guardiola and skipper Vincent Kompany – who both watched from a box at the Academy Stadium.
Chelsea are still on course to win the FA Youth Cup for the sixth time in eight seasons but face a tough test in the second leg against Manchester City.
The Blues have lifted the trophy for the past three years – having beaten City in each of the last two campaigns, winning 5-2 and 4-2 on aggregate.
After a quiet opening spell, Chelsea began to take control as the first half wore on. Ugbo had a shot blocked on the turn and the rebound was fired over from the edge of box by Callum Hudson-Odoi, who then curled another effort against a post after good work by Jacob Maddox.
The breakthrough came a minute before the interval when the impressive Hudson-Odoi burst into the box and, after his shot was deflected against the post by keeper Arijanet Muric’s legs, he teed up Ugbo to slam home.
Both sides had chances in first-half stoppage time, Ugbo bundling over a defender but lobbing into Muric’s arms while at the other end, Jadon Sancho shot wide from a good position.
City’s equaliser came when Chelsea’s Dujon Sterling was caught in possession and Sancho fed hotly-tipped Foden, who burst into the box and finished low left-footed.
Hudson-Odoi went close to restoring Chelsea’s lead but there was no separating the sides ahead of next Wednesday’s return match.