This study examines the antioxidant, anticancer, antimicrobial, and antibiofilm activities of Hydnum repandum, an edible and medicinal mushroom known as sweet tooth or wood hedgehog. H. repandum ethanolic extract had a high amount of myricetin and apigenin and displayed antiproliferative effects against the MCF-7 and HT-29 cell lines. Moreover, the extract displayed antimicrobial and antibiofilm activities against methicillin-resistant Staphylococcus aureus ATCC 43300, S. epidermidis ATCC 35984, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853. Synergetic interactions have been observed when antibiotics such as kanamycin and ampicillin are used together with mushroom extract. The minimum biofilm eradication concentration values were lower for H. repandum extract than for antibiotics. This study demonstrates that H. repandum has antibiofilm potential against biofilms and confronts antibiotic resistance.