Mladečské Cave I, was first excavated by Josef Szombathy, who recorded his visits and excavations to the cave in his diary, a diary which is the sole source of information on the early excavations at the site. Szombathy first excavated the cave on June 7, 1881. The initial excavation ended on June 12. The first human fossil, the skull of Mladeč 1, was discovered during this excavation. Other fossils discovered during this excavation include Mladeč 2, Mladeč 3, Mladeč 7, Mladeč 12-20 and Mladeč 27.

Szombathy's second excavation at the cave started on July 13, 1882 and ended on July 18. He returned again and excavated the cave from August 7–12, 1882. Mladeč 8, Mladeč 9 and Mladeč 10 were discovered during this excavation.

Szombathy named the cave Fürst Johann’s Höhle in honor of Johann II, Prince of Liechtenstein, who owned the land where the cave was located. While the cave lay in the domain of the Prince of Liechtenstein, the cave also partially lay in the fields of a local villager, A. Nevrlý. Thus, the parts that lay in A. Nevrlý's fields were ceded to him.

In 1902, A. Nevrlý built a wall to separate the Liechtenstein entrance from the cave and began to excavate a new entrance to the cave. Along with Jan Knies, a local schoolteacher and amateur archaeologist, the two began to excavate the cave. Mladeč 39-41 and Mladeč 88-91 were discovered by Knies.